A 12.5-metre yacht sank overnight while moored in Cass Bay, prompting a regional council response to protect the environment and navigation safety.

A blue heeler dog named Buddy was on board at the time but was safely recovered and returned to his owner.

Environment Canterbury said there is diesel and other oils onboard the sunken vessel, but no significant loss of oil or fluid has been observed so far.

Debris has been seen in surrounding bays and staff will be collecting it throughout the day.

An Environment Canterbury spokesperson said, “Our team is working to minimise any impacts to the environment and ensure there are no hazards to navigation.

We encourage anyone who spots debris not to touch it, but instead report it by calling 0800 765 588.”