I don't think I can hold my breath long enough to stay down to 30'
I reckon it's why there are so many crannog sites. Those houses sit just offshore enough not to be bothered by midgies, clegs, or other flies. They're cleaner too, and since most seem to have been roundhouses, the conical roof fills with smoke and that kills both insects and any vermin.
Quite fancy living in a crannog at times