Two children had to be rescued from the lake in Queen Elizabeth Park on Sunday after a submerged tree branch holed a hired fibreglass boat.
The youngsters were with their father and all were wearing life jackets.
As a result of the incident, a call has gone out for Masterton District Council to drain the lake and severely trim overhanging willows and remove other debris from the water's edge around the lake's islands.
Queen Elizabeth Park Boats owner Peter Douglas said that about 3pm Sunday a family of seven had hired three paddle boats.
The father, his 9-year-old son and a toddler aged about 1 had been paddling round the larger island when the boat hit a 3m branch which punctured the fibreglass below the water line.