Water is not generally a friend to wood, so when you have wooden floors, you will want to protect them from moisture and associated damage. It is possible to make your wooden floors waterproof or at least water resistant, which will help to stop warping and prolong their beauty.
Fit for purpose
Waterproof and water-resistant are two very separate concepts. When a wooden floor is finished, there will likely be some coating on the top that provides some form of barrier to water. Lacquer or varnish on the wood will provide more protection from water than a simpler oil finish.
There are products available that deliver more protection, but insurance against wet feet is not enough to protect against the amount of water that might be splashed around in a bathroom with a wooden floor, for example. A truly waterproof finish to protect against pooling water will be quite difficult to achieve.
Preparing the floor is key to a good result. Clear the floor, clean it and repair any damaged areas. While you are there, you will probably want to seal up any sources of drafts. For more information on how to do that, see this report from The Guardian.
Sand the floor, starting at the edges with a rougher grade of sandpaper and working up to a fine grit. After this, you will need to clean the floor thoroughly again to remove all dust and debris. Next, apply the waterproofing material that you have selected. Do this on a warm day with a breeze so that each coat can dry completely before the next one is added. At least three coats of resin or polyurethane are generally applied, and you will need to inspect each coat for bubbles or wrinkles and sand them out before proceeding.
Engineered Flooring can be manufactured to deal with these issues. If you want to find out more about Engineered Flooring and its possibilities, you could consult experts in the field such as http://www.woodfloorwarehouse.co.uk/.
Whatever finish your wooden floor has, it is best to mop up liquids as soon as possible. If you are applying a finish to your own floor, make sure you work toward the door so you can leave and allow it to dry without walking on your efforts.