Spoiler alert: this weekend will be hot, again. Sitting inside with the AC blasting in your face gets old quick, so why not take advantage of the city’s extensive and ever-improving waterfront by participating in the sixth annual City of Water Day festivities this Saturday? Take a free ferry to Governors Island or Liberty State Park in Jersey City for boat rides on historical or educational vessels, kayaking, fishing demonstrations, environmental education and advocacy workshops, food from vendors like Coolhaus and Wafles and Dinges, live music, and special activities for kids. Unfortunately, most of the free boat tours are full already, but there are still a few spots available if you move fast. If that doesn’t work, you can make your own boat out of cardboard and packing tape (really!) at the Cardboard Kayak Competition, which begins at noon at Kayak Hill on Governors Island. Better make sure it’s seaworthy, though, because the event culminates in an actual race at 2:15. Gowanus Canal is also getting in on the action with an interactive public boat pond that allows people to see what’s going on above and below the Superfund site’s surface through video cameras attached to remote control boats and aquatic robots.