Arta Beach (Whale Shark Bay)

A shallow bay on the southern shore of the Gulf of Tadjoura, just outside the cliff walled Ghoubbet al-Kharab, where seasonal plankton blooms draw one of the world's densest gatherings of juvenile whale sharks each November to January. The animals here are unusually small — mostly young males of 3-6 m — and researchers suspect the gulf is a nursery, with skiffs sometimes sitting over a dozen sharks at once. Encounters are snorkel first in green, plankton rich water a few metres deep; scuba is a secondary affair on the fringing reefs. The plankton that feeds the sharks also cuts visibility, and Ghoubbet's tidal currents can run hard, but the trade off is swimming alongside the largest fish in the sea at arm's length.