Both Eastbourne lifeboats were launched on Friday afternoon after a yacht was seen speeding along with no crew on the deck.
Passing vessels raised the alarm after the yacht was spotted off the coast of Eastbourne.
Among those raising the alarm was a sail training yacht whose crew said they had seen the 10 metre yacht motoring at speed apparently with no crew on board five miles offshore.
Dover Coastguard was alerted and Eastbourne RNLI station contacted.
Fearing a man overboard, both lifeboats were launched to find the boat.
An RNLI spokesman said, “Lifeboat volunteers found the yacht and discovered two people on board both below deck and the vessel on auto helm with no lookout.
“They were given safety advice and reminded that a fundamental requirement of sailing in crowded waters is the need to maintain a good watch at all times.
“Both lifeboats then returned to station.”
Also on Friday, Eastbourne’s all-weather lifeboat Diamond Jbilee was launched to assist an 11 metre yacht which had suffered engine failure whilst rounding Beachy Head en route to Sovereign Harbour.
At the scene a lifeboat crewman was transferred to the casualty vessel to secure a towline and the vessel was then taken under tow back to Sovereign Harbour.
For more information on the RNLI callouts visit http://www.eastbournernli.org/
While lifeboat crews were out on sea rescues, Eastbourne town centre opticians Specsavers held a fundraising weekend for the RNLI with staff and customers on exercise bikes for charity.