Imagine if as a rite of passage into adulthood, you had to climb Mount Everest while torrents of water constantly forced you back. As impossible might seem, this is essentially what one species of Hawaiian goby must face as it migrates from the ocean to the rivers where it lays its eggs.

The Nopili rockclimbing goby (Sicyopterus stimpsoni) is an impressive little fish that’s endemic to Hawaii and lives as adult and spawns in freshwater, but when the larvae hatch they are swept downstream into the ocean where they develop for 3-6 months before returning to their native island streams. When the juveniles do return, the steep mountainsides of Hawaii are what stand between them and their spawning grounds. While Pacific salmon are famous for leaping gracefully over short waterfalls whilst dodging hungry bears, Sicyopterus is only a few inches long but must nevertheless scale the wall of a waterfall up to 330 feet (100 metres) tall.

Perhaps even more amazing is the goby’s sucker-like mouth that serves as a climbing aid. During a two-day-long process that begins while it is still in the ocean, the Nopili radically changes its morphological skull structure, shifting the position of its mouth from the front to the underside of its head and even forgoing its omnivorous diet to graze exclusively on algae. All of this, coupled with the fish’s pelvic sucker disc that’s formed by the fusion of its fins, serve to turn it into a rock-climbing maestro. The goby is not only rewarded for its heroic climb with safety from the aquatic predators that cannot follow it, but it’s also celebrated in a reassuring Hawaiian saying that “as the Nopili clings, so will luck.”