At the marina I would install a permanent dock ladder .
FarCry beat me to that one. There should be permanent ladders at the marina. It's more common to fall off a pier or dock than a boat.
You also need something on the boat you can deploy from the water when you find yourself there unexpectedly. Or, like some, after diving in and THEN realizing the ladder is up. A folding step on the rudder and two on the transom can save your life. The prior owner had done that on my Pearson 27 and it was handier than the ladder.
Think about bagging a rollable ladder and keeping it stowed in a bag between stantions with a pull line to deploy it from the water.