A private float plane from a fish processing company pulled four people from the wreckage. Another person managed to swim to shore, said State Troopers spokeswoman Megan Peters.
Troopers pulled five bodies from the water after the tide receded, Peters said. The pilot was among the dead, she said.
Four of the survivors are in stable condition at Providence Kodiak Island Medical Center and the status of a fifth survivor is unknown, according to a Coast Guard statement.
No information about anyone on board has been released pending notification of family members.
The plane was headed to Homer, a quick flight north, on the Kenai Peninsula, according to Kodiak radio station KMXT.
The aircraft is owned and operated by Servant Air, a local company that serves half a dozen communities on the large island in south-central Alaska, 225 miles southwest of Anchorage. The flight service started in 2003 as a one-plane operation and has grown to a fleet of seven small aircraft.
A message left for Servant Air owner Terry Cratty was not immediately returned.
The National Transportation Safety Board is investigating the cause of the crash.
