Here photographed in water (in a little container) - fast swimming!
< 3mm (see last photo)
Environment: about 2m above sea level, directly at the seashore. At the limit of a fenced off area with very compacted ground. Same spot in over time: https://www.inaturalist.org/observations?nelat=43.55599523120043&nelng=7.141501727142852&place_id=any&subview=map&swlat=43.555460683734225&swlng=7.140187444725554&taxon_id=435407
Under rocks in shallow water or very close to it.