You can totally do that too.

This is a nice synthetic ocean sound, with "waves":

  play -n synth brownnoise synth 0 0 0 10 10 40 trapezium amod 0.1 30

Or with a little more high end, it sounds like gusts of wind:

  play -n synth brownnoise synth pinknoise mix synth 0 0 0 10 10 40 trapezium amod 0.1 30