It’s nearly impossible to stay put in the sea where waves and swell are meters high. The boat actually does try to stand still, for which they developed their own positioning / thrust system, but the tolerance is something like 3m-6m with the rocket adjusting its path on the fly.

But there are definitely no “static coordinates”, it would have to move a lot more than a few meters for the rocket to miss, and it would be due to trajectory and fuel constraints rather than ability to maneuver.