The 31-year-old scallop diver died after being pulled unconscious from the sea off Methil in Fife on Saturday afternoon.
The alarm was raised after his support crew realised he was in difficulty. He was brought to the surface but died later in hospital.
The second man was recovering last night after getting into difficulties while diving on a wreck of the coast of Angus.
The man, who is in his forties, was surfacing from a wreck at Lunan Bay off the Angus coast when he suffering an attack of the bends.
Police have launched an investigation into the Methil incident. The diver had gone into the sea at the start of his shift, but colleagues became alarmed when no bubbles came to the surface.
Crew members on the fishing vessel Rob Roy issued a mayday call to Forth Coastguard shortly before 2:30pm. Two divers on a nearby catamaran went down to bring the unconscious man to the surface.
A spokesman for the Coastguard and Maritime Agency, which co-ordinated the rescue, said: "The unconscious diver was transferred on to the Kinghorn inshore lifeboat, which had a paramedic and oxygen on board, and was taken into Methil.
"In the meantime, Forth Coastguard had also requested the rescue helicopter from RAF Boulmer to scramble. When the lifeboat arrived at Methil, a decision was made to transfer the diver on to the helicopter and take him to Edinburgh Royal Infirmary."
The diver died a short time later in hospital. His identity has not been released. A spokesman for Fife Constabulary said: "Fife Police are currently investigating the circumstances surrounding the death of a 31-year-old male, who was diving off the coast of Methil this afternoon."
A report is being submitted to the procurator-fiscal.
In the second incident the Red Bay 10, an Arbroath-registered vessel issued a mayday shortly before 1:20pm yesterday after a diver was pulled from the water unconscious.
A spokesman for Forth Coastguard, said: "We sent the lifeboat from Montrose and a helicopter from Lossiemouth which both arrived at the scene at the same time.
"It was decided the situation was not critical and he was flown to Aberdeen Royal Infirmary where the helicopter arrived at 2:50pm. He was then put in a hyberbaric chamber which provides emergency recompression for divers suffering from the bends."
In March, scallop diver James Irvine, 42, was found dead after being reported missing off Lower Largo in Fife.
Last night a leading figure in Scotland's scallop industry said diving was a dangerous profession, but the high prices paid for hand-dived scallops could encourage some divers to take risks.
The source said: "Diving is a health intensive type of occupation and while there are very organised regimes which follow heath and safety rules there are also a number of smaller operators who are driven by the high prices paid by restaurants."