Well, there's a lot of laminate options that actually are more durable than hardwood flooring and do better job repelling water. If you use a rubber walk pad for sound and water emission sealer any good laminate floor will outlast most traditional wood floors hands down.
Water is usually the...
I would do a board replacement. If you have a box of flooring left over you can match the existing floor or if its solid hardwood like red oak or white oak you can replace where the existing register was by blending it in with a board replacement Example of board replacement.