Dennis, from Durban, was swimming in the company relay race and entered the water at 11.22am. There was no record of him exiting the water at any point along the race.
The race organisers were notified by concerned friends who were swimming with him, after they waited for more than an hour for him to emerge from the water.
“Within minutes the missing persons protocols were implemented, resulting in a thorough search of all the medical facilities at the event, as well as double-checking that he was not taken from the water by any of the lifesavers on the water,” said the organisers in a statement.
This year was the first time a new unique tag system, that logs all swimmers as they leave the water at the finish line or when they are taken from the water by the safety staff, was used.
When Dennis was not found, the search was moved to the water.
The swimmer’s family were also notified and they rushed through to Midmar to be close to the search.
At 6pm, the SA Police Service’s Search and Rescue unit, under the command of Lieutenant Jack Haskins, had taken over the command of the search.
They will be using all the possible daylight left on Saturday to continue the search and had already repeated a check of all the land area.