Teaching pre-swimming skills to young children helps prepare them for classes and to learn swimming on their own. It helps to have a pool, but several skills can be practiced in kiddie pools or the bathtub.
For beginning swimmers, there are three things that I like to help develop: comfort level, motor control, and confidence. It is important that the activities are fun, easy going, and non-demanding. Forcing activities could cause aversion to water play, making learning to swim difficult.
Many young children resist getting wet, getting splashed, and having water on their head. If your child is especially hesitant, keep it simple. Play in a water table, splash pad, or small kiddie pool. You could do special activities like washing bikes or the car, play sponge toss, or "paint" the sidewalk with a water bottle.
Bring favorite water-safe toys into the pool or buy special toys just for use in the pool. Sinking toys, although not deep, encourage children to reach down into the water. Being comfortable putting chest, shoulders, and chin into the water will help them be comfortable with more difficult skills later.
Non-swimmers are particularly hesitant to put their heads in the water or even get their heads wet. Use a bucket or cup to pour water on various body parts. Make it into a game by playing Simon Says, Mother May I, or Head Shoulders Knees and Toes. When putting water on their head, begin by only putting water on their hair or shoulders. As they are more comfortable, move closer to the face. Eventually they will be comfortable with water being poured over their head & face.
Keep an eye out for the next topic: Motor Control and how it relates to swimming skills.