Swimmers and surfers along the Southern California coast were interrupted on Wednesday as a sheriff’s helicopter crew calmly warned them to get out of the waters after spotting several great white sharks.

Videos posted by the Orange County Sheriff’s Department showed a beautifully calm, clear blue-green sea...and, on, closer look, several sharks swimming near people at Dana Point.

“Attention, in the water....you are paddle-boarding next to approximately 15 great white sharks,” Deputy Brian Stockbridge announced over the helicopter loudspeaker to people in the water. “They are advising you exit the water in a calm manner. The sharks are as close as the surfline.”

Advisories were also put up for beaches up and down Southern California thanks to shark sightings this week. A woman was even bitten by a shark at San Onofre State Beach on April 29. She survived the attack after a witness intervened in time.

Marine safety officials said frequent shark activity is due to a “thriving aquatic ecosystem” in the area and believe that 10-20 juvenile sharks swam near Long Beach every day.