Sephiroth's vision in the gloom was temporarily dulled by Nozomi's light-spell but thankfully he's not too close so a blink or two later it's returned to normal. In enough time to see the result and immediately conclude that this was the time to move if they were ever going to.

Just as well he doesn't need to switch asterisks again, Sephiroth wills himself forwards in that direction, floating still without touching the water until he's back on the dry part. He flashed a grin at Kuja's comment but other than that, he'll begin to levitate himself upwards back into the room they came from.

Someone might have to steady the rope from above, after all.