I just had one made this year. It''s a midship track mounted folder ladder three sections 70 inches long with 5 steps.
The standoffs fold in and secures to the top lifeline with room to walk past. I think to get aboard from in the water easily you want a nice step and 70 inches. Not that you can''t get in with less but it makes it comfortable.
Our boat has a transom swim ladder that folds in the middle with not much in the water and we carry a dink on davits too. It means the ladder is useless without deploying the dink. This was not a safe situation. The folder was really my only choice and I wanted it easy to get back aboard.
Here is where one can be had:
Note that the quality of the stainless can drastically effect the price. This one is not inexpensive, but is _really_ well made. A cheap chromed steel one won''t last long.