Two Hawaii residents and one visitor agreed to pay undisclosed fines after federal officers caught them harassing Hawaiian spinner dolphins off of Makua Beach on Oahu.

Enforcement officers with the National Oceanic and Atmospheric Administration’s Office of Law Enforcement initially saw the dolphins performing aerial acrobatics, then noticed three swimmers who were apparently pursuing the small pod of dolphins.

The officers watched and recorded the marine activities on video for 15 minutes.

Not only were the swimmers pursuing the animals, the officers observed, but the pursuit was causing some behavioral changes in the dolphins, which included tail slaps, quick changes in direction and the aerial displays.

“Some people go out there knowing that it’s potentially illegal (to interact with dolphins),” said Adam Kurtz, a NOAA Fisheries wildlife management coordinator, in a news release. “These cases serve as a reminder to everyone that there are consequences for harassing spinner dolphins, and it’s possible to get fined if you pursue them in violation of the law.”

NOAA declined to say when the incident happened or what the exact amount of the fine was.

Hawaiian spinner dolphins are protected under the Marine Mammal Protection Act, which prohibits any attempt to harass, hunt, capture or kill a marine mammal. Harassment includes any act of pursuit, torment or annoyance that could injure the animals or disrupt their normal behavioral patterns.

Hawaiian spinner dolphins feed offshore throughout the night and return to coastlines and sheltered bays during the day to rest, according to NOAA, so are vulnerable to disturbance and harassment. For spinner dolphins, NOAA recommends keeping a respectful distance of at least 50 yards.

The officers issued penalties according to its penalty policy for violating the act, which also applies to commercial entities. In 2017 a dolphin tour operator on Hawaii island was fined for illegally harassing spinner dolphins.

Anyone who witnesses a potential violation in Hawaii can call the NOAA Office of Law Enforcement at 800-853-1964 or email RespectWild life@noaa.gov. To report marine animal emergencies, call NOAA’s statewide hotline at 888-256-9840.