A waterproof anti bark collar is highly recommended if you live near water: swimming pool, beach, lake, dam etc. Whenever your dog like playing in the water, the waterproof anti bark collar would still working. In this case, a anti bark collar rates as water resistant or weatherproof is not recommend in this situation. A water resistant or weatherproof bark collar works fine under rains or cleaning by normal water but it is not rated to put under the water or into the water direct.
Waterproof also means the collar is only "proof to normal water", it is not designed to used in salt water. If the collar gets into salt collar, please clean it with normal water as soon as possible.