Half-Gnome Wereshark (5e Subrace)
From D&D Wiki
The weresharks are strange shapeshifters. The half-gnome variety of them are no exceptions. They have aquatic developments as a result of their mixed blood. It is said that they were once of feral origin, which befits most creatures like the wereshark. However, the gnome gods could not leave them in madness, and their intellect and cunning ended up saving them. Their bodies show the aquatic features predominantly, giving them sharkskin, gills, and a dorsal fin betwixt their scapulae. Their form remains humanoid as a normal gnome.