Since this is a la-la thread, why not...
In principle, the rocket can translate as fast as the hydrofoil can move, and so if there's active homing, "it's easy"*
For that matter, the hydrofoil will not tip, tilt, or bob with the waves.
Without any of that, if you want to launch really often (to Mars) and you want to maximize fuel use, then land on a stable pontoon barge that's just sitting off shore, straight into a landing/launch cradle, do a partial refuel, and hop back.
In the sense that other people around here say "it's easy".