MacDuffee’s joints weren’t watertight, so pressure in the suit had to equal the surrounding water, right?
If it is not watertight, what is the purpose of the suit?
Yes, if the pressure in the suit equals the water pressure it would keep the water out. Sounds like the suit is partially water tight so it would keep most of the water out. So the pump just needs to keep up with the water. At 214 feet its about 7.47 atmospheres.
Diving bells work using a similar process.