15W amplifier + 15W speaker + FM modulator + 12V 7Ax2 + an old pressure pot = underwater speaker.
We have tested it at 10 meters. The music is very well heard at a distance more than 30 meters and lyrics clearly audible at a distance of 15 meters.

[video=youtube;rWatolmfzw4]http://www.youtube.com/watch?v=rWatolmfzw4&feature=youtu.be[/video]
We have tested it at 10 meters. The music is very well heard at a distance more than 30 meters and lyrics clearly audible at a distance of 15 meters.

[video=youtube;rWatolmfzw4]http://www.youtube.com/watch?v=rWatolmfzw4&feature=youtu.be[/video]