LOL - I think you probably need to apply a certain amount of interpretation when it happens you live in a very cold place and your puppy is a puppy during the winter

On the other hand, I wouldn't just leave it until the weather warms up either. The point the article is trying to make is that it is actually
important to expose young puppies to a wide range of situations and experiences, most especially those that they're likely to encounter later in life. This helps to create well-balanced, socialised individuals who're not going to get excited, fearful or anything else over new and strange things but rather approach them in a confident and outgoing manner.
In the actual case of water, if its freezing cold outside it's not going to be a great experience for the pup to go diving into a river. But socialising her with positive experience in water is still a good idea. Possibly this could be achieved with warmish water in the bathtub or shower - it's not quite the same, but water games can still help in terms of creating positive associations and dispelling any fear of water.