Wow, nice location! Do you think if it was a uke with water just inside, but played outside the pool, would it sound the same? Any ideas brewing for new plastic water filled ukes?
It does. The water moving inside alters the resonant properties of the body by limiting the movement where the water is pressing and changing the pivot-points for the soundboard's movement. this dampes or enhances the various harmonics of each tone. That is what makes the wah-wah effect. (Wah-wah is also what my daughter calls water, lol) It might not be as pronounced if it's only on one side but it should make a change that you can hear. There are a few points in the vid Mike linked that show it.