This 1998 Cochrane Review looked at pool fencing as an effective method to reduce the risk of drowning in children.
The authors found that, to be effective, pool fences should have a dynamic and secure gate, and should isolate the pool from the house (that is, have a fence that is four-sided).
This review supports the need for legislation to require fencing of both newly constructed and existing pools, and include enforcement provisions, in order to be effective.
Reference: Thompson, D.C., & Rivara, F. 1998. Pool fencing for preventing drowning of children. Cochrane Database of Systematic Reviews, 1998, Issue 1. Art. No.: CD001047. DOI: 10.1002/14651858.CD001047