A FOUR-MEMBER team from the Wong Tai Sin Junior Police Call JPC will leave for Japan tomorrow to compete in an international sand sculpture competition. Champions of both the open and international sections of the Regional Council's Sand Sculpture Competition last winter, the team will represent Hong Kong in the Japan contest, a highlight of the 1994 Higashiichiki Town Harbour Festival, to be held in Kagoshima on Sunday. In the last four weeks, the team had been working hard to map out the design of their entry. Under the advice of experts from the council, the team finally came up with a magnificent sculpture at the Clear Water Bay Second Beach in Sai Kung recently. ''We are under heavy pressure,'' said team representative Wong Yin-lun, adding that the team did its best as it wanted to be on the winners' list. Wong Tai Sin JPC members have taken part in many sand sculpture competitions and have brought home prizes. They were also the first runner-up in the youth section of the Regional Council Competition in 1989.