How the MH370 Flaperon Floated

[Thumpalumpacus]

What if it was tangled in kelp for a while, close to the surface, before being wrenched free by a storm? Has that possibility been explored?

It sounds reasonable, except that the satellite data suggests the plane ended in the Southern Indian Ocean. I presume that's too deep for kelp (a quick google says that kelp grows in shallow rocky coastlines). That's the first time I've heard of the kelp theory.

Another theory is that the flaperon was not submerged but constantly flipping, but that was discounted because of the shape of the flaperon, and barnacles don't like exposure to air for even short periods.

Except that in your post above it is suggested that the flaperon separated from the plane prior to loss. The final resting place of the plane itself would not necessarily be relevant under that assumption.