The parents of two boys who drowned in the Grand Canal a year ago yesterday called on the authorities to lower the level of water in locks during warm spells to prevent children swimming. Mr Christopher Mahon of 15 Glenfield Grove, Clondalkin, told inquests into the deaths of his son , Keith Mahon (13) and a friend, Jason Ryan (10) of 9 Glenfield Grove, that a "no swimming" sign was placed on the lock after the tragedy, but two days ago children were still swimming there. He said the only way to prevent children swimming in the canal during hot weather was to lower the water level so they couldn't get in.The inquests heard that the boys and a number of friends went to swim at the ninth lock in Clondalkin on May 29th 1997 as they had no money to go to the swimming pool. The witnesses said the boys were "messing in the water" before the tragedy.Two firemen skilled in lifesaving searched the lock the lock, which was 75 ft long by 15 ft wide by 15 ft deep. They were said to be hampered by the poor visibility in the water.After some of the water in the lock was drained away, the boys were recovered with a grappling hook. Jason Ryan died later that evening and Keith Mahon was pronounced dead the following day.Post mortem examinations showed that both boys died of asphyxia due to drowning. The jury of three men and three women returned verdicts of accidental death in both cases. The jury also recommended that "no swimming or diving" signs and lifebuoys should be provided by the relevant authorities.