I would have thought it was a fairly simple task to decide whether you needed coding or not. If you are offering yourself as a 'maritime photographer' and covering sporting events, or using the boat directly in that way, then yes, you should be coded.
If it is only you and you happen to have a boat and take some occasional photos from it, then for the hassle, annoyance, irritation and general pain-in-the-ass red tape involved, then I wouldn't bother with coding.
Look at it this way - you go out for a drive, see a stunning sunset, capture it on camera, and you find that there is a market for that stunning picture in an art gallery. Would you feel compelled to re-insure your car for business use?
Basically - if it is a business, do it. If its occasional snaps from your boat, it isn't worth it.