The Dutch Navy is said to have thought up this particularly nasty experience.
The offender was tied around the middle, perhaps with arms free, and hoisted to a yardarm.
A rope had also been tied to the offender and run underneath the ship to the other side from that yardarm.  The sailor was dropped into the water and then pulled under the ship, near drowning and probably being scraped against the barnacle covered bottom of the ship.
A gun was fired during the process, "which is done as well to astonish him so much the more with the thunder of the shot, as to give warning until all others of the fleet to look out and be wary by his harms".    (from Nathaniel Boteler, A Dialogicall Discourse, 1634)  
   
We have slightly revised this punishment.  Some of you may say is unreasonably harsh....  that the orginal Keelhauling was bad enough.  But,  I'm firm believer that the punishment should befit the crime.  

  Panz.......Mister Nasty hisself.    Oh, you brought it on yourself Panz, yes indeedy.  If you examine the photo below, you will see its a picture of what used to be a beautiful red pen.   Yes, Panz  snatched it outta me own lil hand and twisted and bent it beyond recognition.  Nosferato finished it off with a mighty 'SNAP'.    It is a crime too horrendous for KP , Scullery or even the Brig.    And Congratulations Panz....you're not just the first one in for Keelhauling...  you now gonna be in CHARGE of Keelhauling.  A fine fitting punishment for a demonseed named Panz.