A man and a young boy were found hanging on to the upturned hull of their catamaran in Bridlington Bay.
Coastguards received an emergency call at around 4.50pm on Saturday and Bridlington's inshore lifeboat headed to the scene.
The crew of Windsor Spirit were able to help the catamaran upright and stayed with the pair while they sailed to safety.
It came after Bridlington's lifeboat crews had been carrying out an exercise to simulate a search for a person lost at sea.
The all-weather lifeboat and its crew launched and dropped a practice dummy, affectionately known in the RNLI as dead Fred, some distance from the beach.
It returned to shore and then headed out to sea again, with the crew using their navigational sills to find Fred.
Bridlington is due to get a new launch and recovery system for its large boat, Antony Patrick Jones, tomorrow.
Since the boat's arrival last year, a relief unit has been helping to get it in the water, but the new system has been specially designed for beaches. RNLI technicians and trainers will be at the station to assemble the rig and instruct the local drivers throughout the day.