How to get chihuahuas to like swimming?

Both of them CAN swim, they try to swim when we give them baths (before they realize their paws can touch the bottom easily) and we just brought them into the pool today (standing with them just in case) but they don't like it. One of them is a 2-3 year old apple cup and the other is a rescue who is probably a puppy (we've had him since march and he could eat solid food when we got him, but he weighs less than 2 pounds and acts like a puppy) and we are not quite sure if he is a Chihuahua or a min pin.

The apple cup is very overweight so it could be good exercise, he swims right for the edge every time, and once dove off the floatie we were on and tried to swim his way to the edge and jump out (we got him before he got close though)

The puppy(?) is a very strong swimmer (he has long legs) and is more likely to swim towards a floatie or back to a person than go to the edge but I still don't think he likes it very much.

Living close to an open canal, having a pool and going fishing so much I would feel more comfortable if they liked to swim. Is there a way to get them more used to it or do Chihuahua's just naturally hate water?