Here is a link to the report on the recent boating incident in Florida that killed the three NFL / college players. Improper anchoring of the boat is the offical Coast Guard cause, but the details are that they had a stuck anchor and in an effort to pull it free, moved the anchor line to the transom. When the boat was powered forward "it became submerged".
I am not trying to cast blame at the individuals involved - it is a great reminder about anchoring and proper methods to free an anchor. Anyone who has done much boating in PWS has stuck an anchor and thought of ways to pull it free. Let's use this incident to live and learn.