My experience has been that parents being in the pool, splashing water and having fund with toys is a great energizer for the pup to get in. our pool got ready when Bende was almost 5 months old (texas tax day flood has delayed it) and Bende first was nervous around it, wanting me to get out with any method. Costed us a whole new marigold garden he pulled out to get me out of the pool, but i resisted and mom`s boy ended up jumping in from the side to get to me. he became a professional dock diver at 1 year old and competes at nationals, goes into lakes when it is 40 F outside and has a coat on!
Miksa was lucky as he came to a a ready pool. He stepped into the shallow part first and enjoyed it with lots of mom splashing and throwing toys around the shallow area. at some point he stepped out to the part which was deeper for him, first submarined, then came up and started swimming. we practiced every day in the first weekend around 3 rounds of how to get in and out, get toys out and then chew time in my lap on the pool furniture. increased pool time gradually, and by now he goes further in, follows me too, but he does not do a full length pool lap yet.
so my advice is to go slow, keep it playful and positive, see pup`s body language and get them follow u in, just as they follow u on the grass or in the house. once they get a hang of it, they start building their owns stamina and improve at an incredible speed.