A beginner surfski will be about as fast as a decent sea kayak. Any ski much "faster" than a good sea kayak will require a certain level of skill and fitness. If you don't have the required skill and fitness; you will actually be slower than if you paddled a sea kayak. Surfskis are great fun but they are not as versatile as a well designed sea kayak.
Current boats
Epic V10L Ultra, Epic V9 Ultra, Carbonology Sport Boost X LV, Fenn Bluefin, Nelo 510, Fenn XT double, Nelo 600, Expedition Kayaks Azure, Mirage 732.
Previous boats
Spirit PRS, Fenn Swordfish, Fenn XT, Fenn Swordfish S, Think Zen, Epic V10L Club, Carbonology Sport Boost LV