Diver has a walkie-talkie microphone fitted into his helmet.
Various shots show a man preparing for a dive in a river. He fixes a microphone into his helmet and it is put over his head. Commentator explains there is a "two-way field telephone" (walkie talkie) linking the diver with the people above.
The diver goes under the water and we see a man talking into and listening to a radio set (not heard). He then goes down a ladder and passes some equipment to the diver who is cutting off steel piles on the river bed. More conversation on the radio system, then the diver is brought back up to the surface.