my experience w/dogs on boats is not mixed.
i have cats that own me. i'm their servant.
that said, my buddy is the one that brings dogs along that i get the experience of.
1 to 2 golden retrievers. best i can tell, mostly untrained. and mostly not controllable.
this is painful. on the beach, when me and my buddy pull up together for a chat, there's his dogs shaking sand all over my boat, not his. shaking sand on me too. sand is not what i want on my boat or me. if i do, i'll introduce, not someone or some dog doing it.
i remember floating down the missouri river w/ my buddy. side by side chating away. next thing ya know, dog overboard. darn dog went for the shore. full blown concrete blocks. no way to bring a glass boat to shore. after 10 or so min. the dog finally came by my boat, and my buddy came close by and got his dog. that was too exiting. too many deadly options in this scenario. my buddy's always having to do the beach. gotta water the dog.
maybe try a cat.
a litter box that takes up minor room cures any pollution problems. fwiw. cats do swim, naturally
the bad i've found about cats. i think it takes much exposure to a boat. . but after they're acclimated. they're easy.
this cat is only kinda hip. out maybe 50 times.
https://www.youtube.com/watch?v=jdvxxsq2CCA
he don't like the ride to the lake. though i think he knows he's going boating, not to the vet. i use different cars for vet vs. boating.
anyway. imho. i'd go cat vs. dog. dog's will be high maint. cats, they just wanna find a cool place for a catnap.
https://www.youtube.com/watch?v=Ui1tTnTcqJE
and that's on a nineteen ft. boat in white caps. imagine howed they'd react to a larger boat. pretty good i'd think.