Puppies growl when they play. Adult dogs growl when they play. It's all perfectly normal. Ask some of our members here who have more than one dog in the house and they'll tell you that sometimes their dogs sound like they're killing each other, when in fact they're just playing.
Vets are not (usually) experts in animal behaviour...they're experts in animal medical problems. Some vets can't even identify dog breeds. Don't take what your vet says as absolute truth unless it's regarding medical issues and even then seeking a 2nd opinion is sometimes a good idea.
Instead of spraying with a water bottle you could try letting out a loud screech/scream when ever your pup nips your feet/socks and then ignore the dog completely for a while until it's distracted with something else (don't even look at it...and have everyone else ignore it too).
Or you could screech/scream and then distract the dog with something you
do want it to chew on and praise it when it plays with that.
Also, try using a loud "Ah..ah!" instead of "No". It works better, IMO. And remember...always reward the dog for good behaviour.
How old is the pup?
Puppy classes and then obedience training are a wonderful idea (and great for socialisation) and I also recommend getting involved with some sort of activity your dog would like (and you will too) like agility.
Good luck with your pup and I hope you'll post some pictures for us to "Ooooo.." and "Awwww..." over soon.
Cass.