This meetup is for cliff jumping into the Croton River.
There is perfect spot for jumping on the Croton River in Croton on Hudson. You rent a kayak for $20, kayak for about 20 min, the pull it over and climb up the cliff. It's about 25 feet tall. I've done it several times and it's super-fun.
I will be going most Sundays between now and the end of the summer. Time varies because it's best to go at high tide.