I use a long piece of plywood that I cut out and secure to the
cleats on the boat and the dock... allowing them to walk on and off with minimal assist... the board is skinny enough to be hidden under the cockpit cushions when underway...My dogs do not like to swim, so never worried about them wanting to jump over. When heeling they go to the low side for their comfort at angst of the other sailors whom may be onboard......