If your just cruising in the ocean on a sector, your probably not going to notice the weed too much. If you are cracking 25 plus knots and hit a decent amount, your suddenly slow down, or cavitate the fins and slide out.
If you were lucky enough to get a small swell day with 25 knots wind, and small amounts of weed, ie no storms leading up to the event, you could give a foil a good go, but if you hit the smallest tinest piece, you 'll end up coming off in an epic crash, or only be capable of doing 10 knots with a huge effort.
Even Johnno K had to jump off when he saw a sizey weed patch a few km off shore, If your half a chance of winning the event, why would you risk riding something that is likely to have a 90 percent failure rate, and require you to get intense physio work to fix your whiplash from crashing from such great heights.
Go luck to the brave ones, if you can't sit at 30 knots without a care in the world for weed, you might want to find another board.

The Oceanic serious will be fine for raceboards, the weed sits out a few km unless there has been a storm westerly. Ridden a lot out there and never had any problems aside from kiting a day or two after westerlies in winter or a serious 40knot SWer blow