A 15-YEAR-OLD boy jumped into the harbour and drowned after he was beaten by another teenager for stealing his girlfriend, a Coroner's Court heard yesterday. Tam Kin-leung's friend, 15-year-old Chan Yat-fung (nicknamed Sai-lung), said he last met Kin-leung in a North Point park with three girls and three boys on December 30 last year. The six were Law Tsui-sze, 16, Ma Yin-ling, Wong Siu-wah and Chan Koon-cheung, 14, Cheung Kwan-ho (Ah Ho) and Li Chi-man. Sai-lung said he accused Kin-leung of associating with his girlfriend, Wong Siu-wah, and asked him what he was going to do about it. ''He suggested he pay compensation of $5,400. I told him I did not need so much. I only wanted $540,'' Sai-lung said. Kin-leung agreed, but was punched by Chi-man for associating with Siu-wah - his so-called sworn sister-in-law. The group later went to the podium of North Point Estate East to discuss the payment again. Sai-lung said he asked Kin-leung why he had been hanging around with Siu-wah and the boy replied: ''I like it.'' Asked by Coroner's Officer John Halley what Kin-leung meant, Sai-lung said: ''Well, I think he meant he liked her so he tried to steal her.'' Sai-lung became angry and slapped Kin-leung while Chi-man and Ah Ho joined in. This was followed by three slaps from Siu-wah. Kin-leung sat on a stone bench and said he would rather drown than put up with the abuse. He then got up and climbed over a railing next to the harbour. Chi-man and Ah Ho ran over, but were too late to stop Kin-leung jumping. Sai-lung said they threw planks and ropes into the water, but Kin-leung made no attempt to grab them. They left without calling the police. Police recovered Kin-leung's body on January 4. A jury returned a verdict of death by misadventure.