Coastguards have warned people using beaches in Kent and Sussex not to take inflatables into the sea after a series of incidents at Camber Sands.
The offshore north-east wind blew two children and three men offshore in two separate incidents on Sunday, when 20,000 people packed on to the beach.
Coastguards and RNLI lifeboats were called out from Dungeness, Rye, Pett and Littlestone.
The Coastguard aircraft from Manston was also deployed.
Everyone who got into difficulty was safely returned to the shore and a thorough search of the bay carried out.
Dover Coastguard senior watch manager Peter Legg said: "Inflatables are fun, but with an offshore wind like we had at Camber Sands, they can be swept out to sea very quickly.
"If you are using an inflatable, make sure it is tethered to someone on the shore.
"And if you are swimming, make sure you know what the tide is doing so you don't end up out of your depth and a long way from shore."
A total of 17 incidents of people needing urgent assistance were reported at Camber on Sunday, including 11 reports of missing children.
In Kent, two yachts were reported to have run aground off Deal and Margate, where the vessel had to be towed off a sandbank.