Look above at the top of this page....there is a link for photographs. You'll find some really nice ones of the beaches.
They are mostly sand..close to the waters edge you might find some finely crushed coral. Both walkable barefoot...unless your feet are really tender
Some areas will have more turtle grass in the water....typically the farther north you go....the less you have. There is a small stretch up north called Habaneros that has turtle grass....but most of the northern areas are clear.
At any point on the island the turtle grass stops when you go out a couple hundred feet....then it's clear. Just be careful about where you swim or snorkel when you are in town as boat traffic is heavy and it's very dangerous.
Have a wonderful trip!
[This message has been edited by Sandshaker (edited 11-14-2001).]