Fears are growing over two adults and five children considered missing after their 24ft motorboat failed to reach its destination.
Coastguards in helicopters have scoured a two-mile stretch of water off Dorset as lifeboats searched among the waves.
RNLI officials say the Sunseeker vessel Solitude has a white hull and a blue top and was last seen at 6pm on Thursday.
It was making "laboured progress" at St Alban's Head, a land form between Poole and Weymouth - the boat's destination.
Crews put an end to their extensive shoreline search in the early hours of Friday morning, officials said.
Authorities are now calling on the public for further information.
In a statement, an RNLI spokesman said: "The vessel with two adults and five children onboard was believed to be making its way to Weymouth from Shell Bay, Poole.
"It had been towed by the Swanage lifeboat the day before after running aground near Swanage."
Rescue crews performed a radar sweep and searched between the rocks along a two-mile search grid from Poole to Weymouth.
After failing to find the missing people, the lifeboat was "stood down" and returned to the station.
Tony Goss of Wyke Coastguard said the adults and children could already be out of the water after trailing their boat home.
They could "be at home absolutely fine, but there is a concern", he said.
People have flocked to Dorset over the past days to watch the Bournemouth Air Festival taking place this weekend.
On the festival's site, it says there will be a Sunseeker parade, using the same ships as the 24ft motorboat currently missing.
