Extremely rough seas meant that a boat could not get to the scene for two days to try to salvage the stage before it sank.
Potentially, the experiment has enormous significance for the space industry.
SpaceX believes if it can recover those stages and fly them again and again, the cost of access to space could be dramatically reduced.
"No-one has ever soft-landed a liquid-rocket boost-stage before," said SpaceX chief designer Elon Musk. "I think this bodes well for achieving reusability.
"What SpaceX has done thus far is evolutionary, not revolutionary. [But] if we can recover the stage intact and re-launch it, the potential is there for a truly revolutionary impact in space transport costs."
Amos, Jonathan, ed. "SpaceX rocket stage in 'soft landing.'" BBC News. British
Broadcasting Corporation, 25 Apr. 2014. Web. 26 Apr. 2014.