KEY WEST, Fla. (AP) _ A seaplane on a sightseeing tour crashed shortly after takeoff Sunday, killing four members of a South Carolina family and the pilot.

The sole survivor was the family's 10-year-old son, who was hospitalized in critical condition.

The plane banked sharply over two seaside hotels after takeoff, appearing to lose power while flying low toward a busy road and mall. The left wing hit the water and the plane flipped over, witnesses said. Black smoke was seen coming from the engine before the crash.

``He saw he was going to go into the avenue, or the shopping center, so he pulled a hard right,'' said Roger Stetson, who watched the crash from his car. ``I was concerned it would hit us or the bus in front of us.''

Stetson said the first people in the water after the crash tried to right the plane, then they began pulling bodies out.

The Cessna 206 was registered to Key West Seaplane Service, said Kathleen Bergen, spokeswoman for the Federal Aviation Administration in Atlanta.

Four hours after the crash, the plane remained completely submerged upside down, except for one pontoon and part of the tail sticking out of the water.

Killed were Lynn Blackburn, his wife Pamela, and two of their three children: 6-year-old Jonathan and 3-year-old Martha, said police spokeswoman Cynthia Edwards.

The other child, Matthew Blackburn, was in critical condition at Jackson Memorial Hospital in Miami with multiple injuries.

The family lived in Charleston, S.C.

Also killed was pilot Keith Bellows, of Gretna, La.

Key West Seaplane Service flies tourists to the nearby Dry Tortugas islands. There are no roads to the islands.