The Pacific Hagfish is often referred to as the slimiest fish in the sea due to its slime pores that produce copious amounts of colorless slime. This slime serves as a defense mechanism against predators by clogging up their gills, aiding the hagfish in evading threats.

Art and fact by @Squidtoons
[Edited by Nicole Rodrigues]
Reference:
Weinrauch, A. M. & Edwards S. L., Greg G. G. (2015). Anatomy of the Pacific Hagfish (Epatatretus stoutii). Hagfish biology: CRC Press, 1-40.