I googled images of the race and people are paddling modified surf-skis or racing kayak but there are also big fat plastic boats too so I can assume there are two or maybe several classes. What you get, depends on what class you want to compete in. Race boats are very tippy and take some time commitment to learn to paddle but are WAY faster. If you want a not-so-tippy, non-race boat that is still reasonably fast, then a long-skinny touring boat is your best bet.
Here's a list of kayaks and how they are rated for speed. It can be useful as you look for a boat. The rating is just the waterline length/width. The higher the number, the longer, skinnier and faster.
http://soundrowers.org/BoatClasses.aspx
I would find out what the boat classes are if you end up getting a fast touring boat. Better to be in a fast boat in the slow class than a slow boat in the fast class.