I'm 72, reconstructed left acetabulum leaving my left foot numb.. Really numb. And POOR mobility. Can't windsurf anymore due to inability to water start without mobility. I'm a wreck. LOL.. New hip also. Bad back needing surgery but just no time. Surgery would cut into my winemaking and two months sailing on a cat in Tortola. Does that answer your question. I would say Dad is right. He will make it work. My best suggestion is: Take a good boarding ladder with wide steps and deep enough that Dad can step easily on the deepest step. Make it a five step and he will do fine. The provided stern steps ALL SUCK. For us old guys and gals.