You can jump away from the boat and land in water. And you can moved along the yards to get closer to the water.
But the tallest mast is 158 feet and that’s a big jump.
Source: was on a tall ship for a week, and done some cliff jumping
In case anyone's curious, here's a picture of a couple sailors on a topyard [1] - I'm not sure you're easily getting any "horizontal momentum" on that thing while 50m in the air in choppy water. Nevermind the safety harnesses.
https://www.alamy.com/stock-photo-detail-of-main-mast-of-tal...
I think the top yards are not much, if any, wider than the deck, are they? Depending how quickly this happens, you may not have enough time to get across the yard and prepare for a 50m jump into water