Saturday: Boat dives out of Simon’s Town, sites to be confirmed
Mozambique dive trip
We have just returned from a short dive trip to warmer waters. We had five days of really good conditions in Ponta do Ouro, Mozambique, with no swell and almost no wind. The water was 23 degrees most days and on every dive we were amazed by something. Watch the blog for a trip report in the next week or two, and some photos and video from the trip. There’s an album of pictures on facebook already.
Dive conditions and plans
The bay has been treated to winds from all directions in the past week, and there appears to be a huge volume of dirty water swilling around. Some places are really clean and inviting and others not so much.There is some rain in the forecast for Saturday afternoon and a fair amount of wind for Sunday.
I am planning to launch on Saturday but will make a call on where during the course of the day tomorrow as I will take the boat out tomorrow for a good look around. If you’d like to be on board for Saturday’s dives, let me know by email or text message and I’ll keep you in the loop.
What we did find was quite disturbing: a hissing, pulsating patch of water beneath which the rusty wreckage of the Seli 1 lies, very close to the surface. There was no wind and very little swell when we were searching for the wreck, and initially we thought it was a school of baitfish disturbing the surface in that way. Fortunately we approached the spot slowly, because if we’d ridden over the wreckage this would be a different kind of blog post altogether.
We rode around the spot as close as we dared, watching the image of the objects below us on the sonar. The buckled plates of the wreck, where the SA Navy divers did their work with explosives to reduce it below the waterline in 2013, were clearly visible. The wreckage – particularly the shallowest part pictured above – is a definite hazard to any boat with a keel. We couldn’t tell exactly how much clearance there is between the top of the shallowest part of the wreck and the surface, but it didn’t seem to be more than half a metre. I hope it’s more than that, and I also hope that SAMSA pays attention to our request for a replacement marker buoy on the wreckage to warn ships (but considering how many channels of communication I had to try before not getting some kind of error, I haven’t a lot of hope).
The Lighthouse Swim is a 10.5 kilometre trip northwards up the Table Bay coastline, from Milnerton lighthouse to Big Bay. The swimmers plunge through the breakers at Milnerton, which is similar to the start of the Swim for Hope at Diaz Beach, and quite intimidating. This year’s Lighthouse Swim took place on 7 June, and we supported a relay team of four swimmers.
Our job was to keep an eye on their safety in the water (we had a SharkShield on board), and to guide the swimmers along the most direct route possible to Big Bay. Things can go downhill very quickly when a swimmer gets too cold, and it is vital to act quickly if the onset of hypothermia is suspected.
Fortunately there was no wind and the swell was manageable. The water was cold, hovering at 11-12 degrees, and other participants in the race dropped out one by one. Only the fastest individual swimmers would manage to complete the course in such challenging conditions. The conditions were good for relay teams, as members could warm up on board in between dips in the ocean. There was ample hot chocolate to go around. Our team of four were full of smiles and enthusiasm, and did a fantastic job, finishing as the second relay team in 2h45.
Upon arrival at Big Bay, all four team members had to jump into the water so that they could finish the swim together.
We did not quite reach the wrinkly finger clean and cold diving conditions we were hoping for this week. We have launched on every diveable day this week, but the water has remained at around 14 degrees and the visibility between 4 and 8 metres. After the dives today I ran around the bay looking for cleaner water but did not find much. There is some south easterly wind tomorrow which will not be a great help. I am out on Saturday for a private charter but plan to dive on Sunday if there is viz.
Text or email me if you’d like to keep in the loop about Sunday’s dive plans.
How was your summer? Can you recall it? We are far enough into winter that it feels like quite a distant memory, but the summer months of 2014-2015 in Cape Town were memorable for all the wrong reasons! It felt like an endless series of windy days, and we were not able to go diving nearly as often as we’d have liked. South easterly gales raged for weeks on end. Most days boat diving was out of the question, and shore diving was iffy. When the wind stopped, the visibility was appalling. Needless to say the frustration levels of Sun Valley’s resident dive boat skipper were high.
Looking back at what our weather station recorded during this time, it’s clear that the feeling of experiencing endless windy days was not an illusion. These two charts of the wind data from November to the end of January are in knots – to remind you, a wind speed of 10 knots = 18.52 kilometres per hour.
The chart below shows the wind speed and direction for each day in November to January that our weather station recorded data. The wind speed is illustrated in two ways (a bit of redundancy, but easy to read): the colour of each block, and the length of the direction arrow inside the block. So, for example, the first Friday in December (top right hand corner of the December block) was a very windy day from the east.
You can observe several things above. One is that many, many days had average wind speeds of over 10 knots, at which point it is already getting a bit uncomfortable on the boat and tricky/risky fishing divers out of the water. The other is how dramatically the wind started to drop off at the end of January. (If you are wondering why the charts end when they do, the bearing in our Oregon Scientific anemometer packed up mid-February and so that month has a bit of missing data while we waited for a replacement unit!)
The same trend is visible in this chart, which shows the average wind speed each day from November to end January (the red line), and an envelope around it showing the maximum wind speed on that day, and the minimum (which was, at times, zero knots).
Summer is the windiest time of the year in the Cape – refer to my post on wind trends for 2014. Even though it’s colder, we are relieved to be in a season of lighter winds that come from favourable directions (in the north to west quadrant) for False Bay.
We felt quite sorry for them – November and December are historically months of appalling visibility and surface conditions in False Bay thanks to the south easterly winds that prevail, and November always seems to play host to at least one massive storm to top things off! Despite having to work with the worst of what False Bay has to offer, the two of them have produced some incredible images, and I’ve admired their persistence and creativity in dealing with murky visibility and adverse surface conditions. (You can follow them on facebook to get regular updates – Mac and Joris.)
Joris was on the boat just before Christmas, getting some of the final set of photographs that he needs for his reef fish story. On this particular trip he wanted to photograph fish on the hook: False Bay is the site of both commercial and recreational fisheries, land and sea-based. Our aim was to track down a Kalk Bay fishing boat that he’d worked with twice already, but they were nowhere to be found (despite being large and yellow, and despite us searching all the way down to Cape Point)! Hailing them on the radio was futile as they likely did not want to broadcast their position.
As a consolation prize, Joris and his personal shark spotter Brandon were able to spend time in the water with three recreational fishing boats. The first two were at Batsata Maze/Smits Reef at the southern end of Smitswinkel Bay. The crew of both boats were using handlines to catch roman and hottentot. The sea was quite choppy and working in close quarters to a pitching boat strewn with fishing lines was challenging. The fishermen were very kind and co-operative! Brandon’s presence was necessary because Joris was on the surface, absorbed in his work, next to boats that were hauling twitching fish onboard, and throwing back fish guts and bits of bait (basically chumming). All these things are very interesting to men in grey suits.
The third boat we found fishing with rod and reel on Caravan Reef, the large, shallow reef that lies close by to the south and east of the wreck of the SAS Pietermaritzburg. We were now a bit further north in the bay, and the large swell that we’d experienced at Cape Point and Smitswinkel Bay had been modified and reduced on its path towards Muizenberg. It was calmer in the water, though the visibility was still only 2-3 metres. Joris was looking for split shots, with fish half in and half out of the water, and it seemed to be getting easier.
I had a great day tagging along on the boat, but my interest in the scale and nature of the fisheries in False Bay was piqued, and if I manage to find out anything of interest I’ll share it here. Did you know that both commercial and recreational fishermen visit the reefs that we dive on, and remove the fish that we like to look at? Those in the no-take zones are obviously exempt (apart from the occasional chancer or ignoramus), but we found commercial fishing boats inside Buffels Bay in the Cape Point nature reserve, close to shore. There was a fisheries patrol boat close by, but they were not prevented from fishing there. I found this puzzling and troubling, because when we visited the Cape Point reserve as recreational divers, we had to jump through a variety of bureaucratic hoops just to be allowed to drive a boat through the reserve with dive gear on board! Never mind taking fish out of the water! More to follow on this subject – and perhaps Joris’s story will also help us to understand this issue better.
You’ll have already felt this, but here’s a bit of encouragement about the number of diving days as we progress through Cape Town’s brief autumn (OK, I think we’ve already done that) and into winter proper. The average wind speed has dropped, and more and more of the day – on average – is relatively windless. Is there a historical precedent that we can appeal to, and conclude that the weather in late autumn and early winter will be good for diving?
I don’t have a precedent going back more than one year, which may cause you to question conclusions based on it, but I offer it to you anyway. The slice of pie shown below was calculated from our home weather station wind measurements, taken in April, May and June 2014. It shows the average wind speed during each of those months, at each hour of the day. (I’ve previously shown you some other information derived from these same measurements, here.)
We can learn several things from this segment of a circular chart. First, the daily average wind speed during any hourly period in April-June 2014 didn’t get much above 8 knots, which is about 15 km/h. Of course the wind did blow stronger (and less strongly) than this, but this is a chart of the average. Looking at where those bright green slices are on the chart, we can see that during these months, it’s windiest between the hours of 7am and 2pm (just when you want to go diving). Finally, you can see that April was windier than May, and May was windier than June (less green, less yellow, more beige). So conditions for being out on and in the ocean improved as we moved further into winter 2014.
Is it fair to infer something – an expectation – about winter 2015 from this chart? I think it wouldn’t be unreasonable to do so, as long as you’re not too dogmatic about it.
A note on the graph
This is a slice (manually edited out of the original) of a circular plot that I did using code cannibalised and modified from Jason and Doug’s Penang climate blog. I had to reverse the labels for the times of day because I’m only showing you the bottom of the circle. The meat of the plotting function looks like this (thanks to Pretty R):
ggplot(df_summarised, aes(x=month, y=hour, fill=speed)) +
scale_fill_gradientn(colours = rev(topo.colors(7)),name="Wind Speed\n(knots)\n")+
scale_y_continuous(breaks = seq(0,23),labels=c("12.00am","1:00am","2:00am","3:00am","4:00am","5:00am","6:00am","7:00am","8:00am","9:00am","10:00am","11:00am","12:00pm","1:00pm","2:00pm","3:00pm","4:00pm","5:00pm","6:00pm","7:00pm","8:00pm","9:00pm","10:00pm","11:00pm")) +
ylab("HOUR OF DAY")+
ggtitle("Wind Speed by month and time of day")+
plot.title = element_text(lineheight=1.2, face="bold",size = 14, colour = "grey20"),
plot.margin = unit(c(-0.25,0.25,-1,0.25),"in"),
I didn’t want to put the entire year’s data up here in a full circular plot because I think it’s a little too useful to share, if you know what I mean! You can see what a complete plot looks like on Jason and Doug’s blog – examples here and here.
We were able to get in the water twice over the Easter weekend: really early on Saturday in False Bay before the wind, and then again on Monday. Monday turned out to be a great day with very little wind. It was however cold, 9 -10 degrees, and we dived the BOS 400, Tafelberg Reef and the seals out of Hout Bay.
Saturday’s dives were interesting but perhaps not fun in the conventional sense of the word – we two back to back at Shark Alley so a film crew could visit the cowsharks. There was not a cowshark to be seen until the end of the second dive, when the divers encountered two dead sharks with what looked like extensive bite marks all down their bodies. We sent the pictures to one of the local scientists running the sevengill cowshark project in False Bay. She observed that the sharks had not been dead long (their eyes were intact, and these would be the first thing to be nibbled by fish), and that the absence of hooks and typical treatment by fishermen suggested that humans were not involved.
This weekend shows great potential for good clean water almost everywhere. There is no swell forecast, and light winds. On Saturday we are supporting Ned Denison at the Robben Island Freedom Swim so there is no diving planned.
On Monday we are supporting the Swim for Hope around Cape Point, so we are making up for all the windy days that have stopped us taking the boat out this summer.
We will need to close bookings for the trip at the end of April. There are three spots still available – let me know if you want more information. We’re away from 28 June until 4 July, traveling via Durban.
I did a week-long time and motion study on myself. The results were very scary. Besides taking way too long to drink each cup of coffee, I spend 95% of my online time looking at weather forecasts. Of that 95% of online time, I spend 50% of it telling a cat to get off the keyboard.
None of this has helped! It’s a long weekend, winter has not arrived just yet, and we should all be out diving. The weather however has decided otherwise.
I would like to dive every day this weekend, and the backlog of student dives is getting out of hand… But I think that the only safe bet will be for Monday. I will however make a call each morning as to whether conditions will permit safe and enjoyable diving.
Would you like to dive? Let me know by return email or text message, and I’ll keep you in the loop.
Somewhere not too windy, with acceptable swell and some viz. Anyone have the coordinates?
There are still a few spaces available on our trip (28 June – 4 July). By that time – the height of winter – some warm water diving and mild weather will be a pleasure. Let me know if you want more information.
Text me or reply to this mail if you want to dive.
We did not manage any diving last weekend as the boat was scheduled to launch in Gordon’s Bay for the Aqualung Fun Day on Saturday but we were cancelled on Friday evening because of bad visibility on that side. Sunday was a howling south easter day so no diving was done.
This weekend has a forecast similar to last weekend but with a few differences. The 3 metre swell that is in every forecast does not appear to be around as the Atlantic wave buoy registers 2 metre swell at the moment and False Bay was relatively flat today. The wind is another matter… There is however less wind on Saturday, so an early launch in Hout Bay is on the cards. We will dive the BOS 400and Tafelberg Reef. Sunday will be too windy for my kind of diving.
Thanks very much to Jerrel for this week’s photo – taken two weekends ago on a dive to Roman Rock.
There is still space on the Mozambique trip (28 June – 4 July). Remember to book your flights if you’ve decided to join us – get more info from Clare. That is how you will confirm your spot.