ESF has 30 minute swimming lessons in English; I think they have facilities in Sha Tin, somewhere else, and South Island School. Children 3-5 are in the Tadpole class. My son has done two 'terms' and has a great time.
At this stage though it is about becoming comfortable in the water. Some of the other children in his class (only four children total) are able to swim underwater short distances; my son can barely manage to put his head under water.