The RMS Titanic is several miles down with much lower oxygen levels and is noticeably corroding since it was first sighted. It will consist of several unrecognizable lumps in a few hundred years.
But you ignore the fact many remains of many more ancient wrecks continue to exist, even if vaguely.
The only problem here is, having these items doesn’t mean they came from “battle”, or being flooded. Obviously they could be debris from various wrecks or jettison events.
Ergo, the divers are lying, and what they have found, does not really exist?
Or, are you saying that whatever physical evidence is down there is not from 3400 years ago?