If you've ever had a bee land in your beer, you'll know they can't swim. If it were one of Harvard's Robobees, however, it would be a different matter altogether.
The Robobee isn't a new creation, but it has just picked up a new skill: using the same motion that it uses to fly in air, it can now push itself forward through water too. It simply ducks under the surface and then slows its pace, flapping its wings at a rate of 9Hz instead of 120Hz. Other than that — plus a little lubrication on the wings to break the surface tension of the water — it's the same old Robobee.
The tiny robot still suffers the same major limitation as in the past, too: because it's so small — it weighs just 100 milligrams, or 0.004 oz — it can't carry a battery. Instead, it must be tethered to a power source the whole while. Still, a drone that can transition from air to water is a certainly an attractive proposition, and one that you can imagine being pretty useful for everything from search and rescue to spying.