[Latteland]

Did they actually have a plan to divert to water if they knew they couldn't safely land?

They aren't clear about whether it was an accident that they ended up in the water or was it by design. They could have planned ahead for this situation, if they detect that they have a problem and can't do a normal safe landing (the out of control spin) and then they could send it for a 'safe' and hopefully controlled water landing like they did. Or it could just be that it was way off course because they couldn't control it and it was just luck.

[darkport]

It’s by design. The default for all F9 rockets is to land off-shore in the water. Once all the checks are complete and the rocket is “happy” and all systems are performing nominally, it redirects to the landing zone (either a barge or on land).

[Latteland]

That is really cool and makes sense. I continue to be impressed and delighted by spacex engineering and design.