A step up
When we are at a floating dock, our deck is sometimes four feet higher than the dock. I can climb up, but my wife needs a step up. I made this little single step to hang off the shrouds where she can also get a good hand hold. It’s all we need to climb aboard when the deck is way up there.
I made it out of a piece of starboard and a little line with clips on the end. I pad it against the topsides with an old wash cloth. 
I have also seen a “fender step”. This is a small boat fender that has a step cut into one side of it. You also hang it from above. The bonus of this items is that you have a dual purpose for it, it can also serve as a boat fender in addition to the step.
Bill! This is a great site. Love all the ideas you’re sharing with us. We have implemented some of these ideas from your past presentations and will refer to your website often, I’m sure, for further ideas. Thanks for putting in this effort It’s appreciated.