The Gulf of Tadjoura doesn't offer the classic coral garden experience — the reefs here are patchy and in places showing the strain of warming events — but none of that matters once a whale shark the length of a school bus slides beneath you.
Between November and February, juvenile whale sharks gather in remarkable numbers off Arta Beach and around the bay, drawn by plankton blooms that turn the surface water a murky green. Visibility during peak aggregation can drop to four or five metres, which feels disconcerting until you realise the shark is already beside you.
Most encounters happen at the surface or in the top ten metres, so this is genuinely one of the world's better whale shark destinations for snorkellers rather than divers. You don't need a certification to participate, though having one opens up the deeper sites around the Moucha and Maskali islands, where you'll find reasonable hard coral structure, turtles, and occasional pelagic visitors in the fifteen to twenty-five metre range.
Currents in the gulf are generally mild, making it manageable for Open Water divers. Spinner dolphins work the bay regularly, and dugong sightings, while not guaranteed, are credible enough that local operators flag them as a genuine possibility.
Logistics are straightforward but limited. Djibouti City has a handful of dive operators — Dolphin Excursions is the most established — running day boats from the capital. There are no liveaboards operating here. The fleet is small, so booking ahead in high season is sensible. Accommodation ranges from budget guesthouses to mid-range hotels in the city itself.
Go between November and January for peak whale shark density; Open Water certification is sufficient for the island dives, and snorkellers are genuinely well catered for at the aggregation sites.