Stilt fishing is unique to Sri Lanka and is found only on the southwestern part of the island (between Unawatuna and Weligama). The fishermen sit on a cross bar called a petta (although plastic chairs are also used) tied to a thick vertical pole pounded into the sand a few meters from shore. The fishermen wades or swims to his stilt, climbs it and uses a fishing pole and line with baited hook to catch fish. The work is obviously very uncomfortable and his catch is meager -- but might be enough to feed a family or two. More prosperous fishermen will buy boats and nets, individually or with a partner; only the poorest use stilt fishing.
Although the approach looks primitive and ancient, stilt fishing is actually a relatively recent tradition. Stilt fishing is believed to have started around World War II when food shortages and overcrowded fishing spots prompted some to try fishing on the water. The practice now likely survives mostly as a tourist attraction. When you stop to get a photo of them, one of the fishermen "works" the crowd for tips (presumably shared by all) -- much more lucrative than catching enough fish to sell.
It is unlikely stilt fishing will survive much longer. After the tsunami of 2004, many who used to live near the shore were moved inland and up hill, too far from the sea to fish, and have taken up farming. As the country grows wealthier during this time of peace, the incentive to stilt fish is reduced.