1) Punish, old navy-style 2) To rebuke severely 
to punish by dragging under keel of ship
to punish by dragging under keel of ship
to punish by dragging under the ship and up the other side. As in, “Drink all the grog again and we’ll keelhaul ya.”
Punishment by dragging under the ship, from one side to the other. The victim of a keelhauling would be half-drowned, or worse, and lacerated by the barnacles that grew beneath the ship.
• (v. i.) To haul under the keel of a ship, by ropes attached to the yardarms on each side. It was formerly practiced as a punishment in the Dutch and English navies.
To pull somebody under the keel of a ship. Done by using ropes and often as a form of punishment.
Keel'haul` intransitive verb [ imperfect & past participle Keelhauled ; present participle & verbal noun Keelhauling .] [ 3d keel + haul : confer LG. & Dutch kielhalen , German kielholen . ] [ Written also 
To punish someone by dragging them under a ship, across the keel, until near-death or death. Both pirates and the Royal Navy were fond of this practice.
to haul (an offender) under the bottom of a ship and up on the other side as a punishment. · to rebuke severely.
Painful punishment whereby the pirates drag a person side-to-side under the pirate ship and they get cut up by the planks and barnacles from the bottom of the ship