Thousands of visitors will descend upon the tall ships this weekend at Penn's Landing for Sail Philadelphia 2018. They will board them to learn about sailing culture and history, but only a select few will be lucky enough to catch a glimpse of the furriest, cutest crew members of the vessels.

A flash of a tail on deck. Curious eyes peering out from a cabinet. A paw darting out from a dim corner for a moment.

Meet the cats of the tall ships.

>> READ MORE: Everything you need to know about the tall ships in Philadelphia this weekend

There's Leeloo, a small cat who resides on the Lynx, a topsail schooner that calls Nantucket, Mass., home. All black with luminous green eyes, Leeloo has been with the ship for a year and a half.

"We got her when she was very young and she's been with us since," Capt. Donald Peacock, who oversees the ship's educational foundation, said as he scooped her into his arms. She relaxed, curling her spine against his chest.

Cats and ships share a long history, despite the fact that felines have developed quite a reputation for being aquaphobic. The ancient Egyptians took cats on their boats to catch birds in the thickets of the Nile River. Trading ships used cats to keep mice from raiding their food stores. And over time, ship's cats became recognized as intelligent and lucky animals.

(In fact, black cats like Leeloo are considered extra lucky by sailors.)

"Leeloo is a very good crewmate," Peacock said. "The whole crew enjoys her. She spends her days napping on the ship and ventures off to hunt at night. She's really independent that way."

Peacock's son, Capt. Alex Peacock, adopted the cat from the Friends of Strays Animal Shelter in St. Petersburg, Fla. It was not love at first sight when he saw Leeloo in her cage, hanging out upside down. A crew member who accompanied Alex had to persuade him that she was the right cat for the ship because of her moxie.

Peacock said that when Leeloo first arrived on board, she was a little disoriented. The cat would often get stuck below the floorboards of the ship, forcing the crew to conduct extensive rescue missions. But it didn't take too long for her to develop her sea legs. Nowadays, she spends her time snuggling with Alex Peacock, catching birds who land on the ship, and napping in the mainsail.

"I've never seen her fall off the ship," Peacock said. "But she has returned wet a few times."

Because Leeloo is so independent, she has also wandered off, once for 12 days in St. Petersburg. Peacock said that his wife organized a psychic reading to find her, but instead the psychic managed to identify the only crew member on the Lynx who wasn't sold on Leeloo.

"It was me," Marc Melendez, the chief mate, piped up, a little sheepishly. "I'm just not a cat person."

Two ships down, Delaware merchant ship Kalmar Nyckel is also home to a ship's cat named Chester Nyckel, a languid, aloof gray cat who has his own Instagram page.

"His presence alone keeps mice away," said Erich von Hasseln, Chester's primary caretaker. "Chester is actually pretty cautious. He doesn't stray too far from the ship and he always shows up for dinner."

Chester is not the first cat to call the Kalmar Nyckel home. During construction on the ship, the crew discovered a small gray kitten curled up in a toolbox. They named her Toolbox and ever since, the ship has kept one gray cat on board. (Previous gray cats have been dismissed for unbecoming behavior, such as scratching and snatching people's hats from their heads.)

"Having a cat on your ship is a really nice thing, not just because they keep vermin away," von Hasseln said. "But because they're affectionate as well."