The crash happened in the Seldovia Slough in Seldovia on August 26 just before 1:20 p.m., according to Alaska State Troopers.
The victims have been identified as:
Ronald Schmidt, 65, Lance Schmidt, 20, both from San Jose; and Daniel Simons, 82 of Los Gatos. It's unclear how the victims were related.
The pilot, Eric Middlebrook, 68, of Anchorage, Alaska, also died, officials added.
A preliminary investigation determined that a Piper PA-24 was heading to Seldovia from Merrill Field Airport in Anchorage before crashing into the water, Alaskan state troopers said.
At around 6:30 p.m. local time Wednesday, after the tide level dropped, troopers were able to remove the four victims from inside the small plane.
Alaska State Troopers said the victims' bodies were sent to the State Medical Examiner's Office for autopsy.
Their next of kin have been identified.
The National Transportation Safety Board is investigating the cause of the crash.