A team of divers has discovered a new community of what could be the world's rarest fish — the red handfish — potentially doubling the fish's estimated population.

The red handfish (Thymichthys politus) is a tiny fish that wriggles, rather than swims, along the seafloor of southeastern Tasmania's Frederick Henry Bay. Its distinctive red fins look more like aquatic hands. Its range is considered to be small — about the size of two tennis courts — and that makes it difficult to locate the fish and its habitat.

Indeed, the latest dive group had given up on locating a potential sighting when one of the divers spotted a single fish scuttling around.

"It's got to be close to the rarest fish in the world," Institute for Marine and Antarctic Studies (IMAS) scientist Rick Stuart-Smith said in a video published by IMAS (below). "Finding this second population is a huge relief, as it effectively doubles how many we think are left on the planet."

Only 20 to 40 individual red handfish were previously believed to exist.

A rare sight

According to a statement released by the IMAS, a member of the public spotted a red handfish, and that spurred the dive activity.

IMAS partnered with the citizen science project Reef Life Survey (RLS) to conduct a two-day diving survey of the area located a few miles away from the previously discovered group of handfish.

"We were diving for approximately three and a half hours and at about the two-hour mark we were all looking at each other thinking this is not looking promising," IMAS technical officer and RLS Antonia Cooper said.

"My dive partner went to tell the other divers that we were going to start heading in and I was halfheartedly flicking algae around when, lo and behold, I found a red handfish."

It's always when you give up looking for something that you find it, isn't it?

The scientists are excited by the discovery because the habitat for the new handfish is a bit different from the previously known group's habitat, and that may mean good thing for this critically endangered species' survival.

"We've already learned a lot from finding this second population because their habitat isn't identical to that of the first population, so we can take some heart from knowing red handfish are not as critically dependent on that particular set of local conditions," Stuart-Smith said.

Divers just found newest members of the world's rarest fish club
The red handfish had a small population of 20 to 40 fish, but now that has doubled thanks to an accidental discovery.