But back to Eustachian tubes. You must take a course and be certified. But the most critical thing to have working for you is your Eustachian tubes. Think of yourself standing on land with the planet s atmosphere pressing on your head and against your ear drums. You need to be able to force some air from your throat through the inch and a half of Eustachian tube into your middle ear to equalize the pressure against your eardrum.
Nothing subtle about it usually.
But in Bonaire that winter they functioned almost perfectly almost. The 2 of us even left our companions behind one morning to do the Moon Walk a daring dive to 180 feet. We prepared carefully for the Moon Walk. The biggest danger at that depth is nitrogen narcosis confusion and loss of judgment. We carried multiple compasses, watches, and depth gauges because neither intuition nor reason could be trusted.