Europe & Northern Asia (excluding China)
World Registry of Marine Species lists six European species and a Syrian one.
In Europe they are found in a wide range near the coast. It's more that they can "handle" saline environments and sandy substrates than that they need it. The most expansive species, Acaeroplastes melanurus, when found further inland is often associated with plane trees (Platanus) where it can also be found under the flakes of bark.