Since you will be at sea I'd get something that stands up to moisture. That means a weather sealed body and lenses.
This 12.3mp camera out resolves the certain Big 2 16-18mp cameras in a recent test in terms of resolution - D7000 was one and I ignored what the Canon one was.
Here's a 3 day 30,000 jpeg movie. Not interesting but interesting in regard to being able to weather the elements.
http://www.youtube.com/watch?v=ULpSJ0toiKAAlso some German photo group/magazine recently placed this cam as 3rd all time that THEY have tested, competing with full frames.
Also the Nikon D700 is said to be very good at high ISO - if that is your style or needs, not sure about its weather sealing.
I hear Canon might be good too, but what scares me about Canon is their QC ... they've had more recalls/fixes/etc. in the last two years than most other manufacturers, and this is in some of their top equipment.
If you can get a good body and lens from the get go you'd do fine.
Stay away from medium format, large format. They aren't "travel" cameras.
In fact, if you want something more compact, check out the Panasonic or Olympus micro 4/3 stuff. Or the G12 from Canon or P7000 from Nikon. I also hear the Sony A55 is pretty nice.
This post was edited by Solarves on Nov 16 2010 09:38am