Spokesperson Craig Lambinon said crews were sent out at 17:00 on Saturday after reports that a number of fishing boats working the waters of the west coast town had been caught in the fog.

Around 10:30 on Sunday rescuers found a capsized 16-foot fishing boat with two Lambert's Bay fishermen clinging to the upturned hull. Both had severe hypothermia, with the water temperature at 11 degrees Celsius. They were taken to hospital in a serious but stable condition.

''It appears that this was one of the boats that was unaccounted for and she had capsized this morning in dense fog, with four crew onboard who were clinging onto the upturned hull of the boat, but with no life jackets and no emergency equipment to raise the alarm, they drifted at the mercy of the sea in the dense fog.

''At some point the two survivors reported that the [four] men fell asleep and when the survivors awoke their two fellow fishermen were missing and they are feared to have drowned.''

The capsized boat was abandoned at sea. NSRI rescuers took the two survivors, aged about 20 and 50, onboard and began emergency rewarming treatment.

Telkom Maritime Radio Services were broadcasting a warning to boats in the area to be on the lookout for the two missing fishermen and the capsized boat, which was approximately 15 nautical miles north of Lamberts Bay and five nautical miles off-shore.

The NSRI also found the two-man crew of another boat, aged 63 and 64, and took them to shore. On Sunday morning they found the boat Jaws Truly with three fishermen aged 34, 45 and 59 on board. They got back to Lambert's Bay safely with the NSRI’s help.

All other overdue boats had been accounted for. A police dive unit would look for the missing fishermen.

- News24.com