It can be difficult to get waterborne objects to go in the right direction -- just ask any boat captain who has had to fight waves on a choppy sea. However, researchers at the Australian National University have developed a "tractor beam" (really, a wave generator) that would make it trivial for you to float anything to its intended destination. The system creates complex 3D waves that have their own currents, letting you pull a target simply by adjusting the waves' frequencies and sizes. In fact, you can produce any flow you like; scientists in the lab made vortices on demand.
A generator like this wouldn't be useful when dealing with big cargo ships in the open ocean, but the team sees it as very handy for controlling many other objects. You could bring small boats into port, for instance, or contain oil spills without using barriers, burns or chemicals. The invention could be used to simulate challenging sea conditions, too. Any practical uses won't be ready for a while, but there could be a day when you don't have to worry about crashing into the docks (or other boaters) after a sailing expedition.