I prefer a kayak with a wide bottom; less tippy. The type also depends on size of your doggie. If it's a small lap size,probably wouldn't matter. If retriever size ,I would get one with a big area to sit in. I don't like the sit- on- top ones as I don't like getting splashed on from the paddles. I actually find a kayak very stable. I took my goose( George) paddling with me( on a leash). DH thought I was certifiable! LOL!