Two people swam ashore to safety after their light aircraft crashed into the sea near Shoreham in West Sussex.
Multiple 999 calls alerted emergency services to the crash at 3.50pm on Thursday, the Maritime and Coastguard Agency said.
The plane, believed to be a Piper, ditched approximately 10 metres from the shore and the pair on board swam to shore unharmed.
A Sussex Police spokesman said: "Two people are reported to have escaped from the aircraft, believed to be a Piper.
"They swam ashore after the plane came down quite close to the beach and are thought to be uninjured at this time."
Pictures shared on social media showed the plane in the sea not far from a shingle beach, appearing to be submerged except for its tail and one wing. An orange rescue helicopter was on the ground nearby.
Jim Barrow, from Worthing in West Sussex, who took the photos, said he was cycling home when he saw the lifeguard helicopter landing on the beach.
The 48-year-old said: "It's not the kind of place you normally see a helicopter landing so I went round to have a look.
"One guy, who I assume was the pilot, was soaked to the skin but he was standing up and talking on the phone so he looked OK.
"We're used to seeing planes fly over but not like that."
A spokeswoman from the Maritime and Coastguard Agency said: "The UK Coastguard received multiple 999 calls at approximately 3.50pm today reporting that a small plane with two people on board had ditched into the water off Shoreham.
"The Shoreham Coastguard Rescue Team and RNLI lifeboat were immediately tasked, along with the Coastguard search and rescue helicopter from Lee-on-Solent.
"Thankfully both individuals are now ashore safe and well and in the care of Sussex Police and the South East Ambulance Service."
South East Coast Ambulance Service said it dispatched an ambulance to West Beach Road, where patients were assessed.
Neither required hospital treatment.