It needs to be a fun time just like training. And yes wait until it warms up. I really have never encountered a lab that didn't like water except for bath time. I don't pressure them into it. First thing you need the dog to be obedient enough so he will not run wild. I would recommend when he get's a little bit older, now that it's cold, just take him on outings to a field or the woods and walk around with him. This will get him used to new areas and all the different smells so he won't be wide open running around from excitement later on from never experiencing new places besides the yard. Once he has settled down start doing fetch drills with him in the new areas.

When the water warms up I just go to a place where there isn't anyone else to distract them and walk a shoreline. Most of the time they will smell the water and get a drink at first. Then maybe walk in it. After 10 or 15 minutes of just walking I will start a training session of fetch. After a few minutes I start throwing the bumper near the water. Then a foot or two out where they have to step into it. Then gradually further and further. Making a big fuss over him each time he completes the retreive. Pretty soon they are swimming and having a ball.

I have never encountered it. But if that doesn't work they say to walk in the water yourself and do the fetch drills with you getting further back each time so he has to eventually start swimming to bring it back. Everything I've read advises not to throw them in the water. The experts recommend if all else fails to tie a 20 ft lead on them. Get chest deep and slowly pull him towards you until he is swimming.

With chesapeaks I don't go through anything, just throw the bumper out into the water and watch them run, jump and swim. But most of them try to swim in the 20 gal muck buckets I use for their water with just their front feet. They have a much stronger desire for the water than a lab.

You can also buy a plastic kiddy pool and throw the bumper in there, but it's not deep enough for them to swim. It will warm up faster than the river though and get him used to jumping into water. A month or so before you can take him to the river.

Blessings