Grass snake (Natrix natrix)

The Grass Snake (Natrix natrix), sometimes called the Ringed Snake or Water Snake is a European nonvenomous snake. It is often found near water and feeds almost exclusively on amphibians.The Grass Snake is typically dark green or brown in colour with a characteristic yellow collar behind the head, which explains the alternative name ringed snake. The colour may also range from grey to black, with darker colours being more prevalent in colder regions, presumably owing to the thermal benefits of being dark in colour. The underside is whitish with irregular blocks of black, which are useful in recognizing individuals.

(source Wikipedia)