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27 October 2026

A waterfall appears to be a natural barrier for a small fish. Yet certain gobies, including species found on tropical islands, can climb steep, wet rock surfaces to reach pools farther upstream.

Their bodies are adapted for this remarkable journey. Some have a specialised pelvic disc that helps them cling to surfaces, while strong body movements allow them to inch upward against flowing water. The climb may be slow and demanding, but it can lead to habitats that larger fish cannot easily reach.

For these small creatures, the landscape is not simply a river flowing downhill. It is a series of obstacles, resting places and routes to new territory.

Their journeys are especially striking because the obstacle seems so disproportionate to the animal. A cascade that looks impassable to us may be a challenge that evolution has equipped a tiny fish to meet.

Nature rarely solves every problem in the same way. Some animals fly over barriers; others burrow beneath them. These fish have developed another answer: hold on, move a little, and continue upward.

The next time a waterfall seems to divide one world from another, remember that some of its smallest inhabitants may be travelling in the opposite direction.

Rajat Chandra Sarmah, Guwahati, Assam, India, Instagram @rajatchandrasarmah, YouTube: conversewithasmile, email rajatchandrasarmah@gmail.com