I use a length of 5/8" dockline, secured to the rear beam and forward bridle. It has a series of knots tied in it for my hands and knees* to brace against. Smooth line does not give me enough resistance. The dock line easily stretches to suite my body weight and then returns to its former length.

A short length of line at the forward crossbar, tied with a slip knot, keeps it out of the water until needed.

*I don't try to stand using my feet, just kneel on the line instead. That puts me a little over waist high at the deck, then it's a matter of simply falling on board!