Halitrephes maasi is a species of deep sea hydrozoan of the family Halicreatidae. The most recent account of the jelly has been found at a depth of 4,000-5,000 feet near the Revillagigedo Archipelago off Baja California Peninsula, Mexico.
Although not much is available regarding this species, research proves that Halitrephes maasi can be found in diverse settings of waters. The hydrozoan has been spotted in both temperate and tropical waters, and has been found in the Atlantic, Indo-Pacific, Antarctic, Mediterrean, and eastern Pacific. This hydromedusae is typically bathypelagic.