At the top of a waterfall in Hawaii a near perfect fish habitat can be found, but reaching it requires a heroic effort to climb a powerful waterfall - a huge obstacle for these tiny gobies. The goby's pelvic fins are fused into a disc which acts like a sucker, so all this little fish needs is a film of water to enable it to stick to the rock and climb. For some, the journey proves just too long. For others, a rest part way up is all that's needed. Many die in the attempt, but those that make it into the pools above get to feed and breed in safety. Once mating is over, the new generation will be washed out into the ocean and the whole cycle will begin again.