In 26 years of business travel I’ve seen and experienced a lot, from bird strikes to passengers self-upgrading and even one who brought their own alcohol on board and refused to stop drinking it even though they were in first class and the flight attendant was happy to bring them another. But I don’t think I’ve ever seen anything quite like this: an American Airlines passenger with a water bottle in their seat back pocket that was bubbling and had a tube sticking out of it.

On closer inspection, though, it wasn’t just water inside the bottle. There were fish. A passenger on board the flight writes, “I thought it was a soda stream the whole time then I saw 3 fish swim up.”

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These fish would have needed to be in water even going through airport security. Fortunately for the fish there are exceptions to the TSA rule limiting a passenger to 3.4 ounces of a liquid (and each 3.4 ounce container fitting inside a 100 milliliter clear plastic bag). For instance there’s a specific rule allowing you to bring live fish through the checkpoint. The container of water with the fish just needs to be screened separately.

Live fish in water and a clear transparent container are allowed after inspection by the TSA officer.

Here’s a woman who videotaped herself taking live fished she’d purchased on a trip through airport security and onto her flight.

If you’re sitting in coach, it seems like a water bottle is a good way to hold your fish. Depending on the bottle, the plastic can be hard enough not to get crushed. And it fits right into the seat back pocket. This passenger took preparations to the next level – delivering air from a pump into their makeshift seat back fish tank.