When taming, make sure not to trap it. When it comes in contact with a barrier of any kind, sabertooth salmon are spawned in behind it. The salmon will bite it an reset its taming. If you tame it in the open water with no barriers it will tame pretty easy. You can not put berries into your hot bar and passive it or honey. You can not knock it out to tame either.

More Megachelon Taming & KO Tips