The largest known gathering of whale sharks on earth, in peak years 400+ animals in one patch of open ocean, feeding on little…The largest known gathering of whale sharks on earth, in peak years 400+ animals in one patch of open ocean, feeding on little tunny spawn at the surface with mouths agape, sometimes 'botella' vertical-feeding. Manta rays and sailfish in the same water. Called 'the afuera', the aggregation was only scientifically documented in 2006 and is still not fully understood. It sits at the collision of Caribbean and Gulf currents. Mexico caps boats and swimmers and bans touching, enforcement is patchy, so pick an operator carefully. Anchorage: Isla Mujeres harbour / Bahía Mujeres; the aggregation is 15-25nm offshore. Hazards: No site-specific hazards noted, brief normally. Altro