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

Wet Season (June to November)

The wet rainy season at Cocos is the same as on mainland Costa Rica: June until November / early December. Hammerhead sharks are usually fund in slightly greater numbers during this period, as are manta rays. Whale sharks may also be seen.

The seas between Costa Rica and Cocos can be more challenging during this period; and that rougher water and rain leads to lower visibility circa. 10 - 25 metres. 

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)