Giant waves pounded the coast of California on Thursday, causing big headaches but also bringing delight among people who enjoyed the unusual waterfront show.

Waves topping 30 feet broke onto shores up and down the state, prompting stark warnings, such as one from the National Weather Service’s Bay Area division: “The ocean is NOT your friend today!”

High surf warnings remain in effect through early Friday, the Weather Service said, and waves surpassing 40 feet are possible. The coastal unrest was caused by a series of storms with hurricane-force winds brewing over the Pacific Ocean, pushing big swells toward the state.

“Stay away from rocks, jetties, piers, and other waterside infrastructure,” the Weather Service added. “Never turn your back to the ocean!”