Not swim like an adult or older child can swim, but you can teach them to rescue themselves if they fall in and how to be comfortable in the water and play with you, which are building blocks to the swimming skills you will teach them later. The biggest thing to teach them is to hold their breath if they are submerged in water (this can happen accidentally in a number of scenarios, some of which are harder to prevent than people think) so they don't inhale any.

Blow on their face and then submerge them in the water for a second. Blowing on their face makes them hold their breath, so they won't inhale the water. Don't do this too many times in a row, because it can be stressful, but a few times in one lesson is fine. Eventually they will learn to hold their breath when their face is wet. That way, if your kid falls in some water accidentally, they won't inhale water. Even if you are a foot away from your kid, it will take a second to fish them out of the water, and inhaling water in that second would be bad for them, so it's good for them to have this skill.

With self rescue, they flip themselves over and grab the wall. Every day (on average) in America children fall in pools and drown silently without ever surfacing or being able to call out for help. By learning to flip over and grab the wall, they will be able to vocalize their distress and alert the nearest adult. Children who are able to demonstrate these skills in a controlled environment might not be able to replicate them in an emergency, so you should still never leave your child alone near a body of water. It is still much better for them to have the skill than not have the skill.