Police want to speak to the people who set off a flare at Haulashore Island in Nelson, around 10pm on Sunday night.
The incident sparked a Search and Rescue call out, with Coastguard, Surf Lifesaving NZ, and the Harbour Master all responding.
Witnesses described seeing a small dinghy in the area with two people on board about the same time.
Police would like to hear from these people and would like to confirm their safety.