Microscopy
Below two images showing one of the types of cercaria (Austrobilharzia variglandis) which can cause cercarial dermatitis.  Diagnostic characteristics include the following:

• Forked-tail
• Presence of "eye-spots"

Proper identification of cercariae which may cause cercarial dermatitis is best left to investigators with a good background in trematode morphology as well as malacology.