This is an old photo of a Royal Engineer Diver in the 'Standard' Diving dress.
The two guys on the pump would turn the wheels in order to pump air to the diver.
Having dived this myself I can say that it is a very comfortable dive once under water. If the glass steamed up, water could be sucked from a 'spittle cock' and spat onto the glass for a clearer vision.
Note: make sure you have someone you trust working the pump.