Cocos Island is very much a year-round excellent dive location, but there are some seasonal differences.

Wet Season (June to November)

The wet season at Cocos is the same as on mainland Costa Rica: June until November / early December, with rains peaking in September and October. June to November is considered prime shark season with the potential for hammerhead sharks to appear in huge schools. Manta rays are also more likely to be seen during this period. Whale sharks may also be seen.

The seas between Costa Rica and Cocos can be most challenging in August and September leading to rougher sea crossings and reduced visibility. Wet season visibility varies between about 15 - 30 metres. June and July can provide reasonable sea conditions, so offer a good compromise between peak shark action and calmer seas.

Water temperatures range from 24 - 27 ^oC (76 - 80 ^oF). 

Dry Season (December to May)

Again, in line with the Costa Rican mainland, December to May usually comes with a lot less rain, less wind and calmer sea conditions. Whilst hammerhead numbers may be a bit lower, you can better enjoy the schools with visibility up to 35 metres. Whale sharks sightings peak between February and April; and endemic Rosy-lipped Batfish are easier to see. 

Water temperatures range from around 25 - 28 ^oC (78 - 82 ^oF)