Definitely a great spot for swimming or hanging out in the summer. Don't forget, the water is cold, and I mean cold :)
Walking distance from downtown but can also take the bus.
You can play basketball or join the large number of people playing volleyball.
Other than that, lost of people form all ages (but most of them seem to be high High-schoolers) mostly soaking the sun and drinking (a lot).
So do expect to see very drunk people.