He could have called it; there was bound to be something that accounted for the otherwise pointless pool of water down here. Half of the reason why he'd procrastinated so damn hard before making the effort to descend. Of course it's a trap, this whole damn place is a series of them.

Sephiroth slowly levitates backwards, near enough out of sight in the gloom, as the other two tentacles reach for other members of this group. It's obvious then that he's not considered a target. If the creature inhabiting the pool has even noticed him at all; he's not even causing the barest ripple on the surface of the water.

Sure he could switch his Active asterisk again and plunge into the water with his sword and play rescue, making himself a target and trying to sword fight while swimming, but he's pretty much convinced now that isn't how this needs to be dealt with. Besides, why put himself in unnecessary peril?

Instead, Sephiroth levitates himself around a sort-of perimeter where he might guess the monster might be directly under the water and turns to the tile puzzle on the wall. Shouldn't take too much time at all for someone of his prodigious intelligence.