I taught my dog how to swim in
same way described by Anneke, exactly what i did. Buddy is still a lousy swimmer,

but, he
can swim now and
loves the water now. and yeah, having a doggie pal along will easily help your dog learn to swim. OH YEAH, your dog will quickly learn how to swim if you bring another dog along!!!
I lured him a bit further each time, rewarded it, and i had to advance so slowly, as my dog is NOT a good swimmer. Just one extra step and
then back, so he could learn, i can swim, and then touch that ground again, real slowly.
So Buddy could learn where the floor of the lake even
is.
Just one extra step out where his feet don't touch, and
then back.
^Over and over.
and over. To help him gain his confidence, "i can swim, and i
can find that floor again."
Just one step at a time. Over and over...........slowly advancing along.
Now he LOVES it, but, he is always the slowest of all the dogs in our neighborhood lake, always.

Even lil small dogs easily outswim
Buddy!!

I often work on buddy's dog-aggression issues in the water, in the doggie beach area, cuz the dogs are safe from my dog and can easily avoid my dog...
and soon enough, at some point, Buddy gives up trying to catch them all, and just sits there, panting, and watching how dogs are
supposed to play.
and i do use a lifejacket when we swim outside the boat in deeper water in middle of the lake, too, cuz Buddy gets exhausted so quickly when swimming. With his lifejacket, he can float or swim around with us in the deeper parts of the lake, too.