Insufficient sea-room to reef with board up? Then reef with board at least partly down to reduce side-slip, but first furl away at least half of the genoa (if you haven’t already done so), to reduce windage. With a well-organised reefing set-up you should be able to be sailing again within 2-3 minutes, so you would have to be in a very tight spot to have a problem with that, and probably ought to have had the reef in earlier anyway. Easy to say sitting here though!