Askeptosaurus

Askeptosaurus is an extinct genus of aquatic reptile related to the thalattosaurian group. Their remains have been found in Italy and Switzerland.

Description
Askeptosaurus was a very thin, elongated creature, that probably swam like an eel. Its tail was very long, accounting for around half of the animal's total length of 2 metres (6.6 ft), and its webbed feet would have been well suited for steering itself through the water. Judging from its long jaws, it primarily ate fish.[1]

Askeptosaurus probably hunted in deep waters, because it had large eyes suited to conditions of low light. Like ichthyosaurs, it also had a protective bony ring around the eyes, which would have prevented them from collapsing under the immense water pressure of great depths.