PROBLEM: Sound reflects off the water surface. Playing this app through a phone speaker above the water transmits only 0.1% of energy into the tank/pond.
SOLUTION: You must bridge the medium.
1. Surface Exciter (Easiest): Press your phone or a vibration speaker directly against the glass (Aquarium) or plastic hull (Boat/Pond liner). The solid material acts as a bridge, transferring vibration directly to the liquid.
2. Hydrophone/Transducer (Pro): Connect a waterproof speaker (IPX7 rating) and submerge it. This provides 100% transmission efficiency.
3. The Jar Method (DIY): Place your phone in a glass jar, seal it tight, and partially submerge the jar. The glass transmits sound better than air.