WoWDB

This buff comes from  Murloc Costume, a reward for attending Blizzcon in 2007. That year's convention did not offer an online streaming service, so owners of this item either physically attended Blizzcon or purchased the code from someone who did.

Prior to 6.0.2, the suit was a single non-consumable BoA item, so you could mail it around to whatever character you wanted to use it on.  It would grant the transformation buff ( Murloc Costume) to change your appearance; it was not an actual costume that you "wear" like armor.  Since to patch 6.0.2, this item has been added to your account-wide Toy Box.  If you had the item, you may now cast this costume on any one of your characters, anytime, without mailing anything around (you will need to click the item once from your inventory to learn it).  Using it on a character for the first time grants the Feat of Strength  Murloc Costume.

It has no cooldown to reapply, but there is a cast time to use.

The Murloc suit has a unique dance animation.  You can fish, mount, loot and perform most activities in the suit.  It does not break on entering combat, but will break on dealing or receiving damage.  I like to wear it on my healer during raids since heals don't break it, only when I take damage. If it is not broken, it will last for an hour on its own.