Us being able to catch crabs, fish, and muscles out on Castle Island would not have been possible or safe 40 years ago. Before the city built the water treatment facility out on Deer Island the harbor was filled with filth. Raw sewage and trash used to be dumped straight into the harbor making the water polluted and the animals living inside of it sick. Now when you flush the toilet it goes to Deer Island to be cleaned instead of straight out into the harbor. Boston Harbor is now one of the cleanest urban waterways in the world.