sailboats and bay water safety

I love the vibe of all the sailboats that have been hanging out lately. But this morning I wondered about how they handle their waste when they are in the bay for extended periods. I don't see them going out of the bay periodically to dump somewhere far away... are they dumping in the bay or is there a way for them to have someone come empty their tanks and dispose of it?

I realize there is a reality of waste in the ocean when living on a boat, but it seems like dumping in the bay would be a big problem considering all the water activities and food sources here.