Home testing of the SharkShield

One of the joys of having a manoeuvreable, user-friendly little boat is the opportunities that arise to participate in a variety of  interesting events. Lately, we have been doing a number of open water swims; not swimming, but providing boat support to a swimmer who is traversing a stretch of open ocean. Last year we did the Swim for Hope around Cape Point, and the Freedom Swim from Robben Island to Big Bay, and several more of the same in 2015.

We used SharkShields at the Swim for Hope events, and with the increasing number of swims that Tony has been supporting we thought it might be time to invest in a SharkShield for use in these events. The SharkShield is a portable device designed to be worn by a surfer, free diver or scuba diver. It has a long antenna which emits an electric current which is intended to repel sharks. When used for open water swimming, the SharkShield is typically attached to the side of the boat with the antenna in the water alongside, creating a radius of 3-5 metres within which the current can be felt by a shark. If you touch the end of the antenna there is a noticeable pinching sensation, so swimmers have to be careful when approaching the boat.

Tony testing some SharkShields in the pool
Tony testing some SharkShields in the pool

Proper scientific testing of the device in Australia and South Africa indicates that it is by no means foolproof, and does not work in all situations, but it seems to have a certain usefulness if your visiting white shark is in the right frame of mind. The paper reporting the results of the SharkShield tests says:

Our study assessed the behavioural effects of the electric field produced by the Shark Shield Freedom7™. The study was performed in two locations and tested two distinct approach and behavioural situations to assess whether the response to the Shark Shield™ was consistent across behaviours. The electric field did not affect the proportion of static baits consumed, but significantly decreased the number of breaches, and surface interactions on a towed seal decoy.

The authors suggest that since breaching requires significant energy outlay, sharks may be more cautious to mount a breaching attack in the presence of anything out of the ordinary (I’m paraphrasing). Even with knowledge of the device’s usefulness only in certain situations, it still provides great peace of mind to swimmers while they swim in parts of the ocean where sharks are known to be mobile, such as False Bay.

The Freedom7 unit outside its neoprene case
The Freedom7 SharkShield unit outside its neoprene case

Tony was able to examine and test several lightly- to well-used Freedom7 SharkShields to see which of them worked, and what the battery life was like. In the process he shocked himself several times, which provided great entertainment to me and caused some consternation to the cats, who were themselves strolling around alarmingly close to the antennae. The unit itself is filled with something that looks like glycerin, to keep it pressurised and protect the electronics. The red switch at right turns the device on and off, and red and green lights indicate whether it’s on, charged, and functioning. A wet hand applied to the end of the antenna also gives information on whether the device is functioning…

The shark repellent cable that was tested at Glencairn this summer is a massively scaled up version of these retail SharkShields. It is essential that development and testing of non-lethal shark mitigation devices continues, to provide an alternative to measures such as the KwaZulu Natal shark nets, and the French government’s shark fishing activities at Reunion in response to multiple shark bite incidents at the island.

Genius gear: the Wetsac

Using the WetSac
Using the WetSac

Several years ago the wonderful Tami gave me a WETSAC for my birthday. It sounds like something squishy and perhaps offensive, but in fact it is a marvel of ingenuity and designed to improve the lives of divers and surfers and outdoorsmen everywhere. She bought it at a craft market in Hout Bay, and both of us have been hunting for a retailer of this product since then. Recently, I struck it lucky with a well phrased google search (something like “wet bag”).

How many times have you struggled out of your wetsuit on a rough surface (Miller’s Point parking area and Hout Bay harbour, I’m looking at you), hurting your feet, standing on the neoprene and pressing it into the tar? You’re damaging yourself and your gear! Then you toss the dripping, smelly wetsuit into the back of your car – into a box, if you’re organised – and hope it doesn’t spray seawater and bits of grit from the parking area everywhere while you drive home.

WETSAC is here to help. Essentially a mat that converts into a waterproof bag, it comprises a circular piece of tough fabric with a drawstring around the edge. You stand on it to get out of your suit, throw in your gloves, hoodie and booties, then step off and pull the drawstring tight. Toss the bag into your divemobile and don’t worry about remnants of your diving and changing adventures ending up all over the boot. It is beyond convenient. Plus, you can buy it online. Make a note for next Christmas!

(I was not compensated in any way for this post… The thing is just geninuely nifty!)

Newsletter: All the good stuff

Hi divers

Weekend dive plans

Sunday: Launching from Simon’s Town to dive the pillars just off Ark Rock at 9.00 and Tivoli Pinnacles at 12.00

SMBs at Roman Rockac
SMBs at Roman Rock

Conditions report

We are having a great run of exceptional diving. The daytime temperatures are still above 20 degrees, the visibility is in the double digits and so is the water temperature. The viz has improved all week and is currently 15- 20 metres depending on who is looking. One of the divers on the boat today shot some video on the SAS Transvaal where you can see a huge amount of the wreck in the clean water. The second dive was to Roman Rock and it was even cleaner.

On Sunday we will launch from Simon’s Town at 9.00 and 12.00 and dive the pillars just off Ark Rock and then Tivoli Pinnacles. Text or email me if you want to dive.

Permits, permits, permits!

Don’t forget to bring your permit to dive in a marine protected area on the boat. If you don’t have one, you need to take your ID document and about R150 to the post office and ask for a “scuba diving permit”.

Mozambique trip

There are a couple of places left on our trip, which leaves on 28 June and returns 4 July. Consider joining us for some warm water coral reef diving – let me know if you want more information. Booking closes mid May, so think quick!


Tony Lindeque
076 817 1099

Diving is addictive!

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Testing a shark repellent cable at Glencairn

Signage at Glencairn explaining the test
Signage at Glencairn explaining the test

Perhaps you have noticed some new signage and a little wooden hut at Glencairn beach, where an exciting test – of an electronic cable to repel great white sharks – is underway. The cable is a massively scaled up version of the Shark Shield technology with which many surfers and lifesavers will be familiar. The Shark Shield has been subjected to scientific testing, and is effective in certain circumstances.

The risers on the cable are clearly visible at low tide
The risers on the cable are clearly visible at low tide

The cable is a collaboration between the KwaZulu Natal Sharks Board (who would like an alternative to the gill nets and drum lines currently used to harvest sharks and other marine life off South Africa’s north coast), and the Institute for Maritime Technology (IMT) in Simon’s Town, a division of ARMSCOR. Shark Spotters and the City of Cape Town are assisting with the testing phase, which started in November and will continue until the end of March 2015. A permit has been obtained from the Department of Environmental Affairs.

The cable is 100 metres long, and is situated at the northern end of Glencairn beach. Cape Town is an ideal location to test things like this, because Shark Spotters has ten years of shark spotting data that will give a baseline measure for “normal” white shark activity without the cable. When something new (the cable) is introduced into the environment, changes in behaviour relative to the baseline data can be ascribed to its presence. Fish Hoek was originally mooted as an ideal beach to run the test, but the trek net fishermen were concerned for their fishing opportunities and so the test was moved to Glencairn.

The cable is off the end of Glencairn beach
The cable is off the end of Glencairn beach

The cable emits a low frequency electrical pulse that – it is hoped – will repel sharks. The electrical output of the cable poses no threat to swimmers or surfers, but for obvious reasons people are requested to keep clear of it for the duration of the experiment. The cable has electrodes on either side of it, supported by vertical risers that are marked by small orange buoys (so the cable runs down the middle of the rows of buoys in the pictures). At high tide the buoys are below the surface, but Tony took the boat past at low tide and photographed them sticking out of the water.

Shark Spotters will be monitoring the cable from the mountain above Glencairn, and a video feed will also be used to closely analyse the movements of any sharks that approach the cable. The risers on the cable (marked by the orange buoys in the photographs on this page) are semi-rigid, designed to minimise the risk of entanglement of any marine life. As it is the end of whale season in False Bay, there is not much risk of a whale visiting this location. Despite that, a boat and crew are on constant standby should an entanglement situation arise.

There is a full report on the testing phase, with an artist’s impression of the cable underwater, on the Sharks Board website, including a list of frequently asked questions (which should set your mind at ease). There’s also a great post at Round About South that includes pictures of the study area, and of the cable from the KZNSB document.

It’s important to note that this is an experiment, and no additional protection from white sharks is offered or guaranteed while the cable is in the water.

Scuba diving parties for kids

Learning to snorkel
Learning to snorkel

Earlier this month we hosted a scuba diving birthday party in our pool, for a group of extremely excited eight year olds. It was a slightly chaotic but enormously enjoyable day! The boys first mastered the use of snorkels, making drawings on slates while submerged. We were impressed by how well they took to skin diving, and they rocketed up and down the pool like sea otters.

After that they tried out scuba gear, and we were amused by the various ways they found to enjoy themselves. One of the boys kept inflating his BCD because he liked the sound the over-pressure valve made. Another made foamy fountains of water by purging his octo in the shallows. Others seemed to feel like Jacques Cousteau as they explored the pool! We taught them how to inflate an SMB using their spare regulator, and brought out our collection of underwater cameras for them to take innumerable selfies and group portraits that they could take home with them.

Parties like this are ideal for small groups of four to six participants, as they are supervision-intensive and a small group lets each child fully enjoy their turn to try out scuba gear under the supervision of the instructor. A little bit of advance planning is recommended for the purposes of paperwork, so get in touch sooner rather than later if you think this is something your child might enjoy. We can conduct the event in your swimming pool at home if it’s less than two metres deep, or at our pool. We have conducted a similar event at the Virgin Active gym, but that requires special permission. Be warned, the scuba diving bug might bite!

Sketching on slates
Sketching on slates

The PADI Bubblemakers and Seal Team programs are designed for kids aged 8-10, and enable them to master the use of scuba gear in the swimming pool. You can read more about those programs on the PADI website. From the age of 10, children can obtain a Junior Open Water qualification, which upgrades to a full Open Water qualification when they turn 15.

I’ve carefully chosen these photos so you can’t identify the kids, hence their mixed quality! The big kid with the silver hair is Tony.

Christmas gift guide 2014

It’s almost that time of year again. Are you ready to see Santa underwater? I didn’t think so.

Santa diving the Aster
Santa diving the Aster


Consider a Discover Scuba Diving experience for non-divers, and for qualified divers a Refresher, a Specialty course, or a voucher for some boat dives. A False Bay or Atlantic Seaboard photo cruise is fun for the whole family.

Email Tony for prices and more information.

Something to read

Everything you need to know about finding a book related to the ocean can be discovered in our list of most recommended books, and our guide to finding the book you need (on this blog, at least!).

Something to watch

A DVD – either a movie, a series box set, or a documentary – is not a bad gift idea!

Dive gear

Smaller items of gear such as cutting tools, masks, clips and other accessories won’t break the bank. Contact Tony for some ideas and suggestions as to what to get and where to find it.

Keeping it local

Support some local entrepreneurs!

  • Rochelle at Oceanscape sells gorgeous ocean-themed clothing at her online shop.
  • Kerri now stocks a range of ocean-themed jewellery at various markets. Check out Accessories for Aquaholics.

Thinking outside the box

What about a day trip to Cape Point, a donation to a worthy cause on behalf of your loved one (the NSRI is always first on our list), an underwater photo shoot, or (if you take photographs or can find a photographer whose work you like and isn’t too expensive) a framed or mounted picture of some of our local marine life?

You can also refer to Christmas gift guides from previous years (2011, 2012 and 2013) for more ideas. Be safe this festive season!

Thinking of learning to scuba dive? Read this!

Student dives in Maori Bay
Student dives in Maori Bay

This blog has been going for a while, and there’s some content that I’d like to revive – all in one place – as a handy guide for people who are considering learning to dive.

Once you’ve made the decision to learn to scuba dive, you may wonder how to shop for a dive course. If you’re doing it just on price, I think you’re doing it wrong. Scuba diving is a sport with inherent risks, like paragliding or rock climbing. Do you really want to base your decision purely on how much it costs…?

Should you go and buy yourself a full set of dive gear before you do your course (or worse – I made this mistake – as a package with your Open Water course)? Read about whether you should or shouldn’t buy gear, and if you do decide to go ahead, there are some tips on shopping for dive gear that might be helpful.

What’s the difference between the Scuba Diver and Open Water courses? There is a difference, and you should be aware of it!

Many people ask whether children can learn to scuba dive. The short answer is yes – from the age of eight, in the swimming pool, and from age 10 in the ocean. More information can be found in this post about scuba diving for kids.

We also have a bunch of other frequently asked questions, some of which might help you on your way:

Does one need to be a good swimmer in order to scuba dive?

Which certification agency (PADI, NAUI, SSI, SDI, etc) is best?

Should one learn to dive before going on a dive trip, or on the trip itself?

Can one scuba dive in winter?

Isn’t it too cold to dive in Cape Town?



Night dive on the wreck of the Clan Stuart

Before the Clan Stuart night dive
Before the Clan Stuart night dive

This footage is five years old and very grainy, but has some sentimental value to me. Tony filmed it after a night dive on the SS Clan Stuart, which on Friday celebrated (?) 100 years aground in False Bay. It was his first night dive in Cape Town (might have been his first dive of any kind in Cape Town, but I’m not sure) and my first ever night dive. I was pretty freshly qualified as an Open Water diver but still had (have) a lot to learn.

I can see just enough of myself towards the end of the video to note that I have my mask pushed up on top of my head, which is stupid. Don’t do that, kids.

Wind speed on the go

Tony taking a measurement
Tony taking a measurement

We have had a couple of spectacularly windy weekends in a row, and have had the opportunity to immerse ourselves in the weather. We have a weather station at home, and for mobile use we have a WeatherFlow Wind Meter. These are widely used by para-gliders, sailors, windsurfers, kite surfers, and others who need to know what the wind is doing at a particular location. This miniature anemometer plugs into the headphone jack on iPhone and Android devices, and takes wind readings via an app.

The app allows you to save readings, which makes them available on the internet. If you see a facebook post with a wind reading, it’s from our Wind Meter, and Tony is probably on the boat. If the wind is very strong, he’s more likely on land! An example of a recent reading (taken when I snapped the above photo of Tony) can be viewed here.

We find this very useful to correlate wind speed and direction to sea conditions. A southerly wind, for example, is particularly uncomfortable for diving in False Bay. Using his mini anemometer, Tony has been able to establish at approximately what wind speed it becomes too unbearable! One of the effects that global warming is going to have on our local weather in Cape Town is increased windiness, so I think we’ll have plenty of opportunity to play with the Wind Meter and go FULL WEATHER NERD. Watch out…