Sweetheart - the strobes are crucial - its basically flashes (like speedlights but underwater ones - so you call them strobes)
I have a set up of 2 strobes so that I could place them (on long arms) to light the subject from the side rather than head on.
Not even 45 degrees - usually between 45 and 90 degrees kind of thing. Reason being that you want to avoid lighting the water between the lens and subject
as there is particles in the water - and any light shining on it makes it visible, whereas if you only light the subject from the side, you dont get the
interference of the backscatter (particles) and you have no idea how many particles float in water.
Generally - The more particles in the water - the less the visibility to the diver. Some days viz is better than others - in the arctic (or is in antarctic) viz can be many many meters. seasons also has an affect. Depending on the surge, wind, whatever else - you can have sh*t floating and we have had times that viz was so bad - we used to jike that you dont have 1m viz in front of you - but rather 6m behind you
I was only interested in shooting, so I wasnt unhappy, but swimming underwater with a hyge set up - and it is quite bulky - isnt easy or much fun. As a photographer you basically float around and shoot - especially doing macro - you hardly look further than 3m, you just focus on what you shoot in front of you. Very helpful to have a spotter, or two shooting together.
Remember also than colour starts going from around 3m, so if you dont have strobes - you will loose colour and everything is blue - as you might have seen.
Snorkelling has never been my thing - and since I stopped diving - I wont even consider doing that. Especially since I dont shoot U/W anymore. Hey I dont even swim! (not that I could do that well either) I have a swimming pool at home - which I NEVER set foot in.
Warm water diving has so many positives - not least of all the drysuit you dont need and tons of weights - but in Cape Town the water may not be warm - but marine life is so varied and plentiful - it made up in spades.