Abandon ship (pronounced: "ABANDON SHIP!!!!!!") is a message or command used by sailors to prompt evacuation of the ship. Calls to abandon ship are almost always used during times of crisis - such as the ship sinking, or fire beyond the crew's capacity to put it out. Abandoning the ship is always considered a last resort.
Once the Captain or highest ranking person in command gives the order, the message is relayed to the rest of the crew. This is either done through an intercom system (if operational) or by each of the crew members passing the message to one another by yelling it.
Depending on the circumstances, able bodied crew members (traditionally male) attempt to help facilitate the evacuation of the others by allowing the women, children, elderly, or infirmed leave first. If lifeboats are available, they are typically the first given the opportunity to board them.
Pirates tend to follow a different set of rules when it comes to abandoning ship. For starters, their circumstances almost always involve large amounts of guns or cannons being fired their general direction. Pirates can't simply debark in an orderly fashion.
Assuming the need arises to abandon ship, they follow the simple, yet effective guideline of every man for himself. Pirates never have any women or children aboard the ship, so they usually either dive off the boat as fast as they can (and get eaten by sharks), or crowd into the ship's one lifeboat where they row towards the opponents ship to beg for mercy (they usually get imprisoned, and eventually hang for their crimes). The latter is considered cowardice by most ninjas who prefer an honorable suicide over wussified attempts at self preservation.
The fact is that the above is written by a paid ninja propagandist. Pirates never abandon ship because they cannot swim. Hence there is no point in abandoning ship.