Before you consider taking your baby/toddler to the pool you need to look at the facilities around you. Ideally you need to be aware of:
Ideally you want to expose your baby/toddler to water as soon as possible to help build confidence, but six months onwards is normally the best time. Although for babies you do need to remember that:
Ideally you do not want to be taking your baby/toddler to the pool if they have or are recovering from a cold or fever. You also do not want to be taking them to the pool if the have diarrhoea or vomiting. You do not want to be taking your baby/toddler to the pool immediately after they have eaten.
Initially you want to build their confidence in the water. Start by making water fun with games such as ring-o-rosie. Encourage your baby/toddler to feel the water on their face so there is no fear of the water. This can be done by getting them to blow bubbles in the pool.
Alternatively you could sign up for a mother/baby swim class which is more controlled and focused.
If you are taking your toddler into deeper water you may want to put arm bands on them to help build confidence. Encourage your toddler to use their arms and legs in the water by kicking and doggy paddling.
If your toddler becomes frightened try to find items to take their mind off the water, such as goggles, balls or buoyancy aids.