Swimmers have been urged to be on the lookout due to a rise in the number of blood-sucking sea lampreys.
Notorious for their vampire-like behavior, these alien-looking creatures have recently been appearing in rivers and streams across England in alarming numbers.
Sea lampreys - as their name suggests - are typically found in the ocean, but during the summer months they can be commonly found swimming up rivers to lay their eggs.
Their unfortunate reputation stems from their tendency to suck the blood of their unsuspecting victims using a grotesque-looking suction-cup mouth full of tiny, razor-sharp teeth.
Perhaps the most interesting thing of all about these creatures however is the fact that they have remained relatively unchanged for millions of years and are even thought to predate the dinosaurs.
Despite appearances, the sea lamprey is actually one extremely effective and resilient parasite.