Short answer: no.
I'm writing this because recently I've seen the term "waterproof" thrown around by a few sites talking about Toughbooks. The word simply does not apply. There is no such thing as a waterproof laptop. Not in the year 2015, anyway. (update: as of March 2019 there is still no such thing as a waterproof laptop.) Panasonic Toughbooks are among the most water-resistant laptops in the world today, and that's nothing to scoff at, but they aren't waterproof.
Maybe those "waterproof laptop" folks are honestly misinformed. Maybe I'm being pedantic. But hey, there's a fine line between imprecise terminology and outright misleading people.
When we talk about water-resistance as it relates to an electronic device, we want to look at its rating for Ingress Protection, or IP. The Toughbook 31 has a rating of IP65, the best of any commercially available laptop. Let's break down what that means.
Ingress protection ratings consist of two separate numerical scales. The first digit refers to protection against solid particles (dust, sand, etc.) while the second digit indicates protection against liquids. The Toughbook 31, therefore, has a rating of IP six five, not IP sixty-five. To make it more confusing, the two scales are not even. Dust protection is rated on a scale of 0 - 6. Liquid protection is 0 - 8.
The Toughbook 31's level-6 dust protection means it has the highest possible rating against solid particles. It is dust tight. Nothing solid is going to get inside and disrupt the laptop's performance.
Its level-5 liquid protection means that it can survive jets of water spraying it from any direction. Essentially, it's weatherproof. If it were level-6, it could take powerful jets of water, something more like a fire hose. Level-7 is submersion up to a meter deep. Level-8 is submersion deeper than one meter. We might call that "waterproof."
Toughbooks still have a ways to go before they can really be called waterproof. For now, they are simply the most water-resistant computers money can buy.