I think airline captain experience will pull some weight with insurers. Much of aircraft stuff applies to marine. Not 100% overlap, but a good bit. Like the other poster suggested, better than a bartender.
When I went for my first marine policy, I went applied as a mechanical engineer, diesel mechanic and I also had built the boat. The agent had seen the boat while it was being constructed. Policy written with no conditions. Street cred of what ever flavor matters.
But to the OP, do get some time with experienced cap's or owner/operators.
I am now a very experienced vessel operator. Put me in an airplane, and my knowledge gaps will be quite apparent!!!.