Definitions by Funk-4:20

Croc on the riverbank 

This occurs when a turd is released and falls short of its intended target, thus remaining semi-submerged in water on the inside of the toilet bowl,replicating a crocodile on the riverbank.

Judging by the slide marks I'd say somebody left a croc on the riverbank.

Croc on the riverbank by Funk-4:20 September 13, 2015