I wanted to share a little about the challenges of underwater shooting. Certainly it varies on a job to job basis, but apart from the obvious logistic and safety challenges, it is very hard to convince a client of the real needs and time limitations I get a lot of pushback regarding safety concerns ands logistics, lighting needs etc. Working is water is slow, it's just the nature of it, also there is safety to be considered, especially when using light above and underwater. Above water are normal land lights with 208/120V power which needs to be kept dry and also have large GFI units (shock blocks in place) if anything hits water it shuts down power immediately. Underwater lights are very safe, Hydroflex has done a great job with them and providing power is run through a GFI you're good to go.
There are also considerations for water clarity, now some work certainly that somewhat murky water serves the story. This certainly applies if shooting in a lake or in the ocean. Pre planning is critical in the case of open ocean work. Not only the water clarity needed for the project as it can vary by location and with mother nature sometimes by the hour, but having all the logistical safety support and preparation in place. Certainly having an experienced marine coordinator is a must. More on that another time.
Now in a tank situation where water clarity is important, it is critical to be conscious of every element that is added to the water. All dive gear must be clean, talent wardrobe should be washed in fresh water without detergent. Any set elements, props or equipment needs to be thoroughly cleaned. Sandbags should not be used. Stainless steel ball bearing shot bags are ideal. It's amazing how fast the water can cloud up, it doesn't take much to screw things up.
Safety is the next issue and this is a big one, keeping talent and crew safe, Especially when you have underwater sets in place. Also talent is often in clothing which makes it hard to swim and often they are not necessarily "water" people. The other aspect is that quite often they need to be weighted and be supplied air from scuba air supply between takes etc. That means adequate safety divers need to be in place, things can fall apart really quickly underwater. The other factor is the scuba system itself, some training is required to put people on a scuba regulator. Even in fairly shallow water if someone holds their breath on scuba and ascends to the surface they risk air embolism, this is due to the air being delivered at ambient pressure as opposed to surface pressure. Even at 5ft deep this can be a problem So again it's important to have qualified scuba instructors in place. I have been a NAUI Instructor trainer for 20 plus years and my Key safety diver for the last 20 years, Hal Wells is a NAUI course director.
Obviously every situation is different, pool, shooting tank, open ocean all have different needs and safety requiremeets. Certainly some situations can be fairly simple but most are not. So many times including very recently, even with support of the producer the clients themselves don't understand the challenges and decline to pay for what is required for safe water work. They choose to find a cheaper and less safe route. I personally would never compromise safety to save a few bucks, I would decline the job on that basis.