The single-engine aircraft went down about 6 miles northeast of Catalina Island shortly after 1 p.m.
The two people onboard were rescued several minutes later by a Good Samaritan boat.
Drew Naffziger of Garden Grove, his wife Kim and his brother Michael were on their 31-foot Jersey Sport Fisher when they saw the plane go down. Drew Naffziger said he first thought the plane was trying to land on the water, but realized what was happening when he saw the plane had wheels.
"I told my brother, 'This plane's gonna crash,' which it did. When the wheels hit the water, the plane went straight up 180 degrees, tail facing the sky, came back down," said Drew Naffziger. "We rushed over to the plane as quick as we could. When we got over there, we saw two guys hanging on to the wing."
Naffziger said about 10 minutes later, they transferred the victims to a lifeguard boat. He said one of the men had a large gash on his head.
Fortunately for the two crash victims, Kim Naffziger is a registered nurse. They did not appear to have any major injuries.
The two aboard the downed plane got on to the boat, which began heading for Avalon. On the way, they were met by a lifeguard boat, which took the two to Avalon.
The cause of the crash is under investigation.