Freshwater leech

Freshwater leech

Observation - Freshwater leech - UK and Ireland. Description: Leech found in large freshwater (spring water) pond at a campsite. Swam with an S-shaped motion and varied in length from about 1-3cm as it moved. Can anyone suggest what kind of leech it might be please?

Leech found in large freshwater (spring water) pond at a campsite. Swam with an S-shaped motion and varied in length from about 1-3cm as it moved. Can anyone suggest what kind of leech it might be please?