Transcript: Marine speakers are designed for outdoor applications where they might get splashed or rained on or even hosed down. We say they are waterproof because of that. Most of the marine speakers we sell are Salt/Spray/Fog tested for many hours in a wet, salty environment using standards provided by the American Society for Testing & Materials.
That having been said, our speakers are not meant to be submerged and they are not designed to work underwater. Engineering a speaker to deal with the water pressure of submersion is very different than designing one to deal with splashing. Even though most marine speakers can probably handle a quick dip, it will be pretty much impossible to find a manufacturer that says it is OK to submerge their speakers.
This can be a particular problem for hot tubs. If a hot tub with speakers installed is a little too full, the waterline can partially submerge the speakers when a bunch of people get in the tub. That can really reduce the life of the speakers and it is a good idea to lower the amount of water to make sure the speakers aren't ever submerged.
Speakers that are made to be used underwater do exist, but we don't sell them. Those speakers are specifically designed to produce sound underwater and they actually don't sound very good above water.