SpaceX first successful droneship landing - Image credit: SpaceX
On 8 April 2016, SpaceX successfully landed a Falcon 9 first-stage on it's autonomous droneship Of Course I Still Love You.
Here is what that looked like:
After performing the the first successful Falcon 9 landing on solid ground in December 2015, four earlier droneship attempts had been made that were unsuccesful.
The landing occured about 300 kilometers (190 miles) off the Florida coastline.