Don’t set a fixed home point. If you lose signal your drone will activate return to home. If the home point is fixed the drone will return and land where it took off. You can probably see the problem with a moving boat …
Hand catching is a matter of practice and confidence. Overconfidence causes the problem. From experience I can say that a Mavic Air can give a nasty nip and draw blood but (so far) no worse than that. And practice over land until you get confident.
Always fly out into the wind. if you use 40% of your battery on the outward leg you should use less on the return and be able to land with a margin of more than 29% battery left. Also, if you lose GPS the aircraft is still flyable but will drift with the wind. Batter to have it drift back to you rather than away.
A siling boat takes a fair amount of concentration. So does a drone. I strongly suggest you have a second person on board to either sail the boat or operate the drone.
The floats I’ve seen for drones seem to be fine for controlled conditions on a calm pond. I doubt they will work on the Solent in a sailing wind. Something possibly to consider is one of these when the bug for saildroning really bites:
And, last thought - a good sailing wind may be beyond the capabilities of a Mini - check out some of @ianinlondon 's YouTube videos on how to fly a Mini: