What is a deep-sea exploring vessel that starts with a B?

A Bathosphere and a diving bell. The first deep sea exploring vessels were in the shape of a bell and were open on the bottom just like a bell. They weren't able to go as low as we can now because there was no protection from increased pressure. They were lowered into the sea by a cable and had fresh air pumped into it. There was also a radio line so the people inside could talk to the people on the ship.