The Beachcombers(2008)

Divided by the stunning and vast expanse of water that is London’s River Thames, a young pair of shy beachcombers are united by their fixation with metal detecting in search of rare antiquities. They soon strike up a sweet and unique connection across the water and build up a language of signs and signals with which they are able communicate daily. But when one of the pair stumbles across a chance discovery, it gives them the ideal opportunity to finally cross over the river.

Official site