Staff at the Balclutha Centennial Pool called the Fire Service shortly after 4pm, when the boy was discovered trapped in the pool, with his head above water.
Pool staff, including a lifeguard, kept the boy calm while waiting for the Fire Service to arrive.
Balclutha Volunteer Fire Brigade station officer Daryl Forrest said the 10-year-old boy slipped his knee between the bulkhead and the pool edge and was trapped for nearly 15 minutes.
Mr Forrest said he managed to slide the boy's leg free shortly after arriving.
Clutha District Council corporate services manager Alan Dickson said the council, which owns and runs the pool, would be investigating the incident.
The pool was closed for about half-an-hour while the boy was freed.
The boy's mother said he was ''OK'' and she took him to Clutha Health First for a check-up.