The only three styles that have an epoxy coating and are waterproof up to 10 ATM:
In order to make one of the above watches waterproof, the crown must be screwed/pushed in all the way so that water does not get inside the casing. See video below. Be sure to do this before exposing your watch to water and always rinse with freshwater immediately after if you expose it to saltwater.
*Please note that water damage is not covered under the 1-year Manufacturer's Warranty if these instructions are not followed and the watch is not one listed above. All other styles are "splash-proof" but are not meant for the water.