A soggy laptop is a dead laptop, unless you can get it completely dry before turning it on—then it might have a chance. The better bet is to not get it wet in the first place. MSI announced a couple of backpacks that might help in that regard, one more so than the other.
MSI's new Mystic Knight and Urban Raider backpacks are both water resistant, a designation that typically means you're okay if you get caught in the rain for a short spell, but you should probably (definitely) take it off before swimming (it's not waterproof). That said, the Mystic Knight ups the ante with a built-in rain cover to keep the bag and your gear inside dry, "even in the pouring rain."
These are both 25-liter bags that can fit up to a 17-inch laptop. They have additional room for other accessories, things like a keyboard, mouse, and headset. The Mystic Knight also sports a roll top that can be used to expand the capacity of the main compartment. It comes with a detachable strap to convert it into a messenger-style shoulder bag, if that's your preference.
Both bags also feature red reflectors, because the only thing worse than getting your electronics wet is getting plowed by a motorist. OK, maybe it's not the only thing that's worse, but it certainly ranks up there.
The Mystic Knight ($139.99) and Urban Raider ($119.99) are "now available" at Amazon and Newegg. We couldn't find product links at either retailer, but we imagine they'll be up before the end of the day.