Strangest Things Found Inside Forgotten Scuba Tanks

When we think of scuba tanks, we usually envision the silent guardians of underwater exploration—clean, pressurized cylinders filled with breathable gas. But what happens when these tanks are left behind, forgotten in garages, basements, or sunken wrecks for years? Surprisingly, scuba tank can become unintentional time capsules—and the strange discoveries inside them range from puzzling to downright bizarre.

Here are some of the strangest things found inside forgotten scuba tanks:

Alien-Like Sludge and Microbial Colonies

In many abandoned tanks, especially those stored in warm, damp environments, scuba techs have discovered thick biofilms and gelatinous sludge clinging to the interior walls. These aren’t just moldy leftovers—they’re entire ecosystems. Scientists have even taken samples from neglected tanks to study extremophile bacteria that survive in low-oxygen, high-pressure, metallic environments. One tank opened in a Florida dive shop revealed a pinkish, syrupy goo that turned out to be a thriving colony of iron-eating bacteria!

Seashells and Tiny Crustaceans

You’d think a sealed tank wouldn’t be a haven for marine life—but if it was improperly stored or had a faulty valve, nature finds a way. One diver recounted discovering tiny hermit crabs and baby shrimp inside a tank that had been used in shallow coastal waters and left with the valve open. Somehow, during storage or transport, seawater (and stowaway sea creatures) got in—and they set up camp.

Homemade Modifications and… Marbles?

Sometimes, it’s not nature sneaking in—it’s humans being curious (or reckless). One tank brought into a service shop had a suspicious rattling sound. Upon inspection, technicians found a small collection of marbles, ball bearings, and even a rusty toy soldier. The diver had no idea they were inside—possibly left from a childhood prank or an attempt to "clean" the tank with abrasive materials. Whatever the case, it was a reminder of why proper inspection is critical.

A Mystery Bone Fragment

Perhaps the eeriest find came from a scuba shop in Southeast Asia. A diver dropped off an old tank for recycling, and while depressurizing and cleaning it, staff found a small bone shard wedged deep in the cylinder. It was eventually sent off for analysis. Though never conclusively identified, experts believe it belonged to a large fish—or possibly a small mammal. How it got there remains a mystery, fueling local ghost stories to this day.

A Message in a Tank

In an odd but touching twist, one tank was found with a sealed plastic capsule inside. Inside the capsule? A hand-written letter from a diver who had passed away, intended for whoever opened the tank next. It was a tribute to the diver's love of the ocean and a reminder to protect the marine world. The tank now sits on display at a diving museum in California.

Forgotten scuba tanks may look like rusty old gear, but they can contain surprises that boggle the mind and spark the imagination. So next time you see one gathering dust—proceed with curiosity and caution.