Four divers died as the result of an attempt to clear old cars
March 15, 1997, Central Washington
Four divers died as the result of an attempt to clear old cars from an irrigation siphon. The first two divers broke through ice to enter the 40-degree water; one wore a drysuit, and the other wore a wetsuit. Each recreationally-trained diver had one tank, and they also had a shared emergency tank. They had planned to connect towlines to the cars that had been washed into the siphon from a connecting canal.
When the divers had not yet surfaced after an hour, two rescue divers were sent in after them. Apparently also underestimating the conditions, this team, too, failed to return. A third team was sent in, finding the second team 200 feet back in the tunnel, and the first team 788 feet into the tunnel.
All four divers died because they had run out of air in the overhead environment.