Hot Tub Speakers.
Speakers and Audio for hot tubs and swim spas.
Brands can be Waterway, Poly Planar, Aquatic AV and Marinavox
Marinavox high quality marine audio for spas and hot tubs.
Marinavox are best know for the subwoofer, The Spa Bullet.
There are numerous other speakers used in hot tubs, that don't really have a brand.
They are used with OEM's in the US and China.