I could think of a wave as a lullaby.
For it makes me happy while being in a complete rest position.
The water is very dear to me, not only because it is the basic thing that we daily use.
But, it is a kind of thing that always gives magic to my day.
Every time I had a night swimming session, it works like a sleeping pill to me, too.
It helps me to sleep deeply & soundly right after that session.