We too have a Jack Russel...Cap'n Henry. He loves the boat and loves to sail. He mastered the companionway like a pro. Except the time I had put in the lower part the hatch in. It's a dark plexiglass that he didn't realize was there. Stopped him in mid air! He fell in the garbage can next to the steps. Had to be there!
I love the breed; though I don't have one. If there is a dog most like me it is the Jack Russell, I figure. I knew they'd like sailing. How long have you been away from land with a Jack Russell? How large of a boat? Ever go outside of the US?
What do you do when the rush of the water going by and a good meal aren't enough distraction? Got crate?