I have gone to the opposite extreme with cameras, I like the idea of compact, and I do carry around a Canon D10 waterproof for quick shots. However, when it comes to getting consistent quality shots, still nothing beats a quality SLR, good lenses and a flash.
I end up carrying around a Nikon D700, 2-3 lenses (a super wide angle 12-24mm is my standard lens in a boat) and an SB600 flash, all in a Pelican case. The 1520 case is a bit of overkill, size wise, but it is a hangover from days when I used to carry a 80-200 2.8 in the kit as well. When choosing a case for an SLR, I would recommend sizing it to fit the camera with an accessory flash permanently on the camera. This cuts down a whole lot of mucking around when you dive in to grab the camera for quick shots.
The benefit of the case is that they are virtually indestructible - I've held my hilux rear axle off the ground with the case standing up (long story, would have taken a photo but the camera was still in the case!). We have even used them as raised casting platforms on fly fishing trips. The downside of the case is that they are heavy and bulky, but as far as I can see it is the only way to guarantee the safety of an SLR camera on a boat.
I think which way you go really comes down to what your priorities are out on the water. If the only time you pull out a camera is when a fish is being landed, then stick to a small compact. If you are in the habit of putting down your rod specifically to take photos, even right in the middle of a hot session, then an SLR will be worth pushing your weight limits for. Plus, if you want a proper wide angle lens to get up close and personal with your subject and really make the pictures stand out, the only way you can do it is with an SLR. Another way of looking at it is if you want a record of your trip, then modern compacts do an awesome job, but if you want to get your pics in a magazine on a regular basis or want to explore the art of photography, then pro-style compacts like the Canon G series or better still a full blown SLR is pretty much the way to go in my opinion.
In regards to the polarising lens issue, I used to use them 100% of the time in a boat, until purchasing the 12-24mm lens. This is so wide angle that it can't shoot with a polariser at any wider than 24mm or it cuts in at the edge of the shot. I've found that not using the polariser makes little difference to most of the 'grab and grin' style shots. Where you do miss it, is when shooting a fish swimming around in the water - the polariser cuts down substantially the amount of glare on the water surface. Usually I make a dash for another lens I keep with the polariser on for in-water shots. Another reason that people use polarisers is to make the colours look deeper and richer. These days, with the quality of editing programs available, it is pretty easy to duplicate this at home. In fact most quality cameras deliver as standard the rich, punchy colours that we used to really have to work for back in 'ye olden days' of film.
Duncan
