Well, much would depend on your lighting conditions wouldn't it? I mean, is he drowning in daylight or evening time? If at night is he in a location where his drowning is illuminated by artificial light? Is there a vessel nearby that you could hail down and ask that the point a beam of light in the water? Does your camera have a flash, and if so, is his struggle within range of your flash?
I haven't even begun to explore other variables such as color versus black and white film, or slide versus print and so on.
I'm afraid your question is much too broad, Pete. I'd ask you to reconsider it and resubmit with some carefully thought out detail so that we could answer the question using reason and logic. Thank you.