If you could take a measuring tape in the water and go to a swimming pool or somewhere where you could check how high you could comfortably have the lowest step, that would be the best way to be sure.
I have a transom ladder on this boat, but I also have a portable ladder that hangs off the toerail from midships for use in choppy conditions.
I hang lanyards to clip on my BC/tank and weightbelt and goodie bags so I don''t have to climb the ladder with all that gear. Once I am on deck I pull it up after me.
Make sure you can deploy your ladder from in the water, just in case you unexpectedly find yourself in the water.