Hi
Apple Watch Series 2 models can be worn when shallow water swimming, including in the ocean.
After wearing Apple Watch Series 2 in the ocean, be sure to clean it by gently rinsing it with warm tap water. The watch and band should be dried using a soft, lint-free cloth.
Apple advises cleaning your Apple Watch if it comes into contact with substances that may cause damage, including sand.
Note that leather and stainless steel bands are not water resistant, so should not be worn in the ocean.
More information and instructions: