What is good film for underwater photography?

I have recently purchased a Nikon Nikonos V camera and am wondering what film would provide the best results.

Have you already had a lot of experience of UW photography?

If not, don't worry about the film type at this stage, since it won't make a significant difference to your results if your camera technique still needs work. Concentrate on the basic rules of UW photography, such as:

-- Dive around midday (10 am to 2 pm) and/or stay shallow (less than 12 m, 40 ft depth) to maximise ambient light (especially if you haven't got a strobe)
-- Get as close to your subject as possible -- at anything more than 2-3 m (6-8 ft), even a strobe will be ineffective
-- Get below your subject, and shoot upwards to make it stand out against the (blue) background
-- Bracket your shots around the 'ideal' settings generated by your exposure meter, to compensate for film batch variation
-- Note down the particulars for each shot (date, subject, film, shutter-speed, F-stop, strobe?) while you're still underwater
-- Transfer this information to a photo-logbook after each dive, so you can start to get a feel for what works in various situations
-- Be prepared to throw away most of the photos you take, especially in the initial phases of getting to know your new camera

And bear in mind that the Nikonos V was aimed at the professional (or at least, highly knowledgeable amateur) photographer -- it was never intended to be used as a simple 'snapshot' camera. You have to decide before you dive what kind of subjects you hope to photograph (e.g.macro vs.divers vs.wide-angle), and set the camera up accordingly (lenses, strobes, etc.). Once you're down there, you don't really have the option of switching subject types mid-dive.

If you already know this and do this, then using a specific film brand will make some difference to the final quality. Most professional UW photographers have long since gone digital, but if you look back through old dive magazines (as I did last weekend, coincidentally) you'll see many recommendations for low ISO (50 or 100 = sharper pictures), high colour saturation (e.g. Fujicolour) film.

That said, ISO choice is really a question of what effect you're aiming for (although I would avoid ISO 200/400 -- unless it's cheaper than 50/100 and you still need practice). David Doubilet has produced some fantastic B&W underwater shots using ISO 1000 or higher (see http://www.daviddoubilet.com/portfolio/default.asp?catid=1 for examples).

Some photographers also advocate(d) using slide film, since the colours tend to be better, but I don't know how feasible it is to make prints from slide film these days.

Whatever you choose, you'll want to use 24- or 36-exposure film, and a new roll for each dive, to maximise the number of shots you can take per dive.

All the best.