Many marine varieties breathe through a siphon, that is, a tubelike organ protruding from the head. The siphon enables them to suck in water through their gills.
Daudzi jūras gliemeži elpo, sūcot ūdeni pāri žaunām pa sifonu — caurulītei līdzīgu orgānu, kura atvere atrodas gliemeža galvā.