A group of swimmers harassed and aggressively pursued a pod of wild dolphins in Hawaii, authorities say

• Hawaiian authorities said on Tuesday that they had referred 33 people to law enforcement.
• The group of swimmers harassed a pod of dolphins off the coast of the Big Island, authorities said.

Hawaiian authorities announced on Tuesday that they had referred 33 people to US law enforcement after a group of swimmers harassed a pod of dolphins in Hōnaunau Bay off the coast of the Big Island.

The state's Department of Land and Natural Resource (DLNR) said that it initiated the case against the group after it discovered them swimming close to spinner dolphins on Sunday morning while officers were on a routine patrol.

Under the Marine Mammal Protection Act, it is illegal to "harass" marine mammals, which is described as the pursuit, torment, or annoyance of a marine mammal in the wild that has the potential to injure it or disrupt its behavioral patterns.

It's also against federal law to swim within 50 yards of spinner dolphins in Hawaii's nearshore waters.

The DLNR released drone footage of the incident, which shows the group swimming toward the retreating dolphins. The department described the swimmers as "aggressively pursuing, corralling, and harassing" the pod.

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It added that officers with the department's Division of Conservation and Resources Enforcement (DOCARE) alerted the group while they were still in the water.

When the swimmers returned to land they were met with uniformed officers.

State and federal officials have since launched joint investigations.

According to the National Marine Fisheries Service, a federal agency that is responsible for the stewardship of the US' national marine resources, spinner dolphins have a "very specific behavior pattern."

The marine mammals rest in nearshore areas of Hawaii during the day in preparation for nightly foraging, which means that daytime swimming near them can reduce their rest period.

This can lead to the dolphins becoming distressed, it said.

The Associated Press noted that while dolphins may appear to be awake during the day because they are moving, they may actually be sleeping even when gliding through the water.

This is because they sleep by resting half of their brain and keeping the other half awake to surface and breathe, the news agency said.

If deemed to have broken the law, the swimmers could be issued with penalties of several thousand dollars.