Sri Lanka Traveler guide

Especially on the beaches of Sri Lanka, it is a close possibility that a leech (or more!) will cling to you.  When this happens, remain calm!  Do  not try to brush them off wildly, 'cause you don't want them to expel the dirty contents of their stomach in you.

A practical remedy would be to bring along some insect repellent with you to the beach, so you can just spray on them and then they will drop down willingly.  However, if you don't have one and the need arises, you can try to gently pull them away, downwards from the head.