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It depends on how you plan to use the ladder. I you are into watersports and swimming, you probably will want a design with a three or more steps and with a short platform if it doesn't interfere with the motor/drive operation. Unfortunately, most of what I've seen are made of tubular aluminum or stainless steel and are and feel flimsy. I have these designs on my boat both front and rear.
I have a friend that found a uber strong step (made from solid rod aluminum) that he put on his fishing boat (rarely uses it for other activities) called The Rescue Step. I've never seen such a robust and simple design before, It is designed to also be deployed from the water in case you fall out and have no one to help you get back in. Seems like it has a very low profile when it is in its stowed position.
Not sure if this style is what you are looking for, but here's the link to their website if you're interested.