As my boats have grown in size and weight (MacGregor 25, Catalina 30, Tayana 37, Kelly-Peterson 44), I've become keenly aware of the momentums and forces involved. Back in the MacGregor and to a lessor extent the Catalina, you could easily shove the boat around by hand. Coming in a little fast? No Problem, just jump off and shove against the lifelines. Now, part of my welcome aboard briefing to new guests is to never, EVER let any part of their bodies get between the boat and anything else.