Abstract: Disclosed is a pier including a deck supported by an array of piles by means of flexible lines extending between the deck and elevated points on the piles. The lengths of the flexible lines extending between such points and the pier are adjustable by reels used to retract or pay out flexible line to raise or lower the deck relative to the piles. The operation of the reels may be carried out selectively or automatically in response to the changing level of the surface of the water relative to the piles. A water-motion powered motor may motivate the reel operation. The deck may be anchored against downward motion relative to the piles by locking apparatus normally engaged in a closed configuration, or by locking apparatus which is normally open and closes in response to the flexible lines going slack.