NSW boy's body found near drain

Police say rushing water caused by heavy rain was a factor in the death of an 11-year-old boy at a park in the NSW Illawarra region.

Ryan Teasdale's body was discovered in a creek bed at the end of a stormwater drain in Unanderra about 11am on Friday.

He had gone missing a day earlier while bodyboarding down a hill at Riley Park with his brother and friends, about 500 metres from where his body was discovered.

His 13-year-old brother raised the alarm about 4.30pm, sparking a frantic search which carried on until after midnight.

Superintendent Zoran Dzevlan told reporters the heavy rainfall and subsequent torrents of water rushing through the drains overnight were factors in the boy's death.