[Jigsaw John]

A commercial airliner departing LAX over the ocean would be at least 3500 feet

Outbound departures take off much lower than that, and hit the shoreline at an altitude of about 500-700 feet. From the runway to the actual waterline is about a half a mile, depending on which runway is used.

[adamsjas]

Outbound departures take off much lower than that, and hit the shoreline at an altitude of about 500-700 feet. From the runway to the actual waterline is about a half a mile,

You need to go out to an airport sometime. Half a mile past the end of a runway most airliners are pushing through 2500 or better. Nobody is flying at 700 feet half a mile past the runway. Most exceed that before even getting to the end of the runway.

757s rotate about 1700 feet down the runway and climb out at about 15 degrees.

So you can see that by the time it traveled the length of the runway (guesstimating 10,000ft) it would be way higher than 700 feet.