Poachers, including a known gang associate from Hamilton, were fined and had dive gear and a vehicle seized after locals alerted police to suspicious diving off Mt Paku in Tairua on Saturday.
The four divers were fined a total of $2750.
The 150 paua, 284 kina and five undersized crayfish seized were returned to the ocean.
Whangamata Sergeant Will Hamilton says the result was "down to luck and good police and MPI team work". MPI chief compliance officer fisheries, Jason Howat, says it was a warning to poachers to expect to be stopped and inspected at any time.
"People who continue to abuse our fisheries will be caught and dealt with accordingly."