There are many ways to improve your surfing when the ocean is flat. Cross-training, gym exercises but nothing is more fun than riding a skateboard. You can do it in the skate bowl, the skatepark or just on your way to work.
Nowadays there are many skateboards that try to make skateboards that ride like surfboards so here is a short overview:
Carver skateboards have been used as a training tool for surfers for a while. They have multiple surfskate models from 25 to 42 inch. They are promoted by (former) top surfers like Sean Mattison, Josh Kerr and Taylor knox. Kerr has his own 28 inch model but check out their cruisy longboards as well.
Smoothstar skateboards (see featured image) are specially designed for surfers. They help to improve your surf technique through improved back leg strength and balance. Their secret weapon is a technically engineered turning mechanism attached to the front trucks. This allows you to turn beyond the ability of a normal skateboard and practice maneuvers such as cutbacks, bottom turns, tail slides and aerials. Laura Enever is a team rider.
The Carveboard has been available for almost 10 years and its main objective was “to create a board, which enabled beginners to pros, the ability to work on their surfing or snowboarding when the snow melts or the surf is flat”. They are the ultimate carving machine with extreme rail to rail capabilities. It is promoted by multiple pro surfers like Dan Malloy and Brad Gerlach. Check out also their other skateboards Long Stik and Surf Stik.
Longboards are good for long skates, cruising down the beach or doing your groceries. They have a cruisy feel to it and you can even practice your cross step on some of them. Sidewinder, Carver and Revenge have great trucks for these boards to mimic the surf action. They help your balance and flexibility and you will practice bending your knees by leaning into a carve. There are many manufacturers but check out longboards from Sector9, Loaded, Original and Maki.