Water Slug

Removing salt from seawater is energy-intensive. Nonetheless, the water slug does it, perhaps as a byproduct of an internal microbial reactor that feeds on waste in seawater.

A hydrophobic plastic bulb that protects the slug from rapid dehydration by saltwater.

The slug's water bulb hosts a highly productive plankton species, turning light into food. Fresh water may be necessary for the plankton's chemistry, or it may be a prison—a way to keep the plankton from leaving.

The water slug's developed beak has a sharp cutting surface. Possible evolutionary history as a parasite or commensal, tapping a host's blood and filtering out toxins. Assessment: only nearby source of drinkable water. Advise fabricator cook before drinking. In case of kidney problems, consider allowing the water slug to feed on your blood.