Tomales Bay is a great place to enjoy the thrill of downwind SUP. Spring winds generally come from the NW which will generate some nice bumps down the length of Tomales Bay. Beautiful landscape, warm(ish) water, abundant wildlife, absence of boat traffic and other hazards, make Tomales Bay an ideal location to surf whitecaps. If you have never gotten your board to plane then you are really missing out! Downwinding combines the best elements of surfing, racing, and touring. If you want to try it, go to Tomales Bay. It's always best to go with some experienced people. You can find them by joining the DownFrienders group on Facebook.
In the meantime, take a look at the map showing some important locations on Tomales Bay. Enjoy all that Tomales Bay has to offer but please be smart! Check the forecasts, go with small group, match the conditions to your experience and fitness level, and always wear a leash and PFD.