We cruised for 3 years on our 28' boat with our beagle, Toby. He was a great boat dog, particularly as he hated swimming (means he would not jump off) and was a good watch dog (would bark at passersby, helpful when in less-secure areas) but a wonderful friend and companion.
he used to stick his head
through the porthole over the galley
and lick up the steam that was rising from whatever was cooking
. . . friends would call him the trophy dog as his head
just fit through the port!
We are about to head off again, this time with kids
on the same 28' boat - the 2 beagles we have now are likely not going with us due to space restrictions, although that decision is not yet final!