Re: cd player
Marine grade cd players are easy to find...West Marine has had a JBL player/speaker package for $99 for the last year. Similar deals can be had right here on iboats.
The true marine units have the electronics weather proofed (sealed), and are the best choice in salt-water conditions. Many boaters use a car unit for fresh water use, and are resolved to replacing somewhere down the road. Marine speakers are the only correct choice regardless of where they get used, since they are designed to handle any moisture issues.
In short, since the marine units can be had for so little, it doesn't (in my opinion) make any sense to do otherwise. With a little shopping around, you can find one that accepts an ipod...that eliminates the skipping that a CD will encounter while cruising.
Happy boating!