I've sent my share of balls into the Desert Forest at Desert Forest.
I've hit a Boulder at The Boulders.
I've been in the pines at Castle Pines (North).
I've been in the walking stick (cactus) at Walking Stick.
Lastly, I did hit two (!
) onto the beach at Pebble Beach. But both were on the tenth hole, so that's Carmel Beach, not really a particularly pebble-y beach. Maybe still counts?