Two adults and five children are believed to be missing after their 24-foot motorboat failed to arrive at its destination.
Coastguard helicopters probed a two-mile stretch of water off the coast of Dorset, while lifeboats scanned the seas.
The Sunseeker vessel Solitude, which has a white hull and a blue top, was last seen at 6 p.m. on Thursday, according to RNLI officials.
At St Alban’s Head, a landform between Poole and Weymouth – the boat’s target – it was making “laboured progress.”
Officials say they finished their lengthy shoreline search in the early hours of Friday morning.
Authorities are now seeking additional information from the public.