SpaceX was unsuccessful in its rocket landing attempt
The rocket did successfully launch the Jason 3 satellite, but on its return trip to Earth it came in harder than expected and one of its landing legs broke.
Unfortunately the live feed of the landing cut out.
But SpaceX said it will release footage of the landing attempt soon.
The launch of the satellite into orbit however, which was the primary objective of the mission, was successful.
In December last year, the company successfully pulled off a land-based landing, but landing a rocket at sea is much more difficult. The target is smaller and isn't completely still as it's tossed about in the waves.
On Monday, Musk tweeted that these kind of drone ship landings are "needed for high velocity missions."
High-velocity missions are mainly commercial launches, when the Falcon 9 has to carry a payload higher than it would on a cargo mission to the International Space Station (ISS). This Jason 3 satellite launch is a high-velocity mission, so that's why SpaceX had to attempt to land the rocket at sea.