Глубиномер https://ru.wikipedia.org/wiki/%D0%93%D0%BB%D1%83%D0%B1%D0%B8%D0%BD%D0%BE%D0%BC%D0%B5%D1%80_(%D0%B8%D0%B7%D0%BC%D0%B5%D1%80%D0%B8%D1%82%D0%B5%D0%BB%D1%8C%D0%BD%D1%8B%D0%B9_%D0%B8%D0%BD%D1%81%D1%82%D1%80%D1%83%D0%BC%D0%B5%D0%BD%D1%82)