What kind of boat are we talking here? Do your friends live the majority of their time on the boat, or are they just wondering if they have a suggie if they can possibly take it with them sometimes on a boat? This will be a HUGE determining factor here.
Either way, I would not IMO. I can't help but wonder - WHY? One reason I wouldn't - what if they get out? I know it SEEMS like a big if, but it's really not. Think about it - what if they do get out? Where will/can they go? Either in the water or inside the boat - neither would seemingly have a positive outcome. One wrong jump when they're out of the cage and they're gone. If they end up in the water how can you possibly save them? If they get out and get into the interior of the boat, I don't see how you would get them out safely, esp if you were already on the water at that time. Also, what about their diet
? My suggies are on BML and that depends on a freezer of some sort. If the fridge on the boat goes out, then what? If one of them gets sick, then what? Also, there's usually quite the aray of smells when on a boat - strong fuel fume smells beign a big one (not to mention I wouldn't take my suggies NEAR a campfire b/c of the smoke alone). This isn't really something I'd wany my suggies around. Just some things to think about... HTH!