I will start from a post by @Edward3c in another thread
What @BLACKCRUSADER didn’t make clear was the courses being talked about are income streams for commercial agencies, like PADI. In BSAC’s training these skills are part of the core syllabus. For example, when doing a night dive, which is one of the experience dive options (see below).
• Shore dive – a dive beginning and ending on the shore
• Small boat dive – a dive from a boat of less than 9m overall length, using a backward roll entry, and where exit requires removal of equipment in the water
• Large boat dive – a dive from a boat of greater than 9m overall length, and where exit does not require removal of equipment in the water
• Boat dive with mechanical lift – a dive from a boat equipped with diver lift
• Nitrox dive – a dive where the nitrox mix is greater than 23%
• Dive using shot line – a dive using a shot line as the only visual reference for descent and ascent
• Wall dive – a dive along a vertical or near vertical wall with no solid bottom a minimum of 4m below the divers
• Dive in protective clothing – a dive wearing either a wetsuit or drysuit
• Low-visibility dive – a dive in visibility ranging between 2m and 4m
• Drift dive – a dive in water moving at between 0.5 knots and 1 knot. Students must have successfully completed modules ST1, ST3 and SO
• Night dive – a dive during the hours of darkness
• Cold water dive – a dive in water where the overall temperature is below 10°C
And to finish, most BSAC trainees do all their open water training in drysuits. By default we issue them a drysuit cert in case they ever want to hire a drysuit.