Well this is just about the WORST way to celebrate the end of Shark Week.

Two men and a woman went to the San Antonio Aquarium in Texas on Saturday afternoon . . . and they grabbed a three-foot horn shark out of its tank.

Then they swaddled it in a blanket like a baby . . . put it in a STROLLER . . . and walked right out with it.

And it was a damn good heist, because the staff at the aquarium didn't realize the shark was missing for 45 minutes.

The cops have surveillance footage of the thieves and they're trying to track them down . . . but everyone's worried about the shark's chances of surviving.

Horn sharks can only survive out of water for maybe an hour or two, and they need to be in warm saltwater . . . so if the thieves didn't have a tank ready for it nearby, it could be in serious danger. 

(Deadspin) 

(Here's a surveillance shot of the thieves.)