They went diving in a marine reserve, grabbing crayfish for an end-of-year office party. They surfaced to find fisheries officers waiting.

But Canterbury real estate agents Dougal Boyd, 58, of West Melton, and Benjamin Rhys Donaldson, 30, of St Albans, hope to escape convictions for their actions in Akaroa Harbour's Pohatu Marine Reserve on December 5.

Their case was in the Christchurch District Court on Thursday, where Judge Tom Gilbert received their guilty pleas, but did not enter convictions.

JOHN KIRK-ANDERSON/STUFF Harcourts real estate agents Dougal Boyd and Ben Donaldson went diving in Akaroa Harbour's marine reserve for crayfish for an office break-up party.

Defence counsel for both men, Jonathan Eaton QC, asked for a remand for a hearing on whether they should be discharged without convictions for their "genuine mistake". One of the men has a family bach in the area and the other grew up nearby.

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The Department of Conservation signalled diversion (which allows people to avoid a conviction) for illegal fishing in marine reserves may have to end, because it believes offenders are not getting the message.

JENNIFER EDER / STUFF Top Christchurch lawyer Jonathan Eaton is representing the two agents. (FILE SHOT)

Prosecutor Susan Newell told Judge Gilbert: "A large number of offenders have been diverted, but the offending only seems to be increasing. Deterrence is required."

Eaton said the pair did not pay enough attention to the signs at the jetty marking where the marine reserve was, when they launched to dive for crayfish. The pair surfaced and saw the fisheries officers, then co-operated fully. The men have no previous convictions.

"They were shocked, amazed, and surprised to find that they were in a marine reserve," he said. The rock lobsters were all returned to the water alive and no harm was caused.

CARYS MONTEATH / STUFF Real estate agent Dougal Boyd in 2005.

The men were "embarrassed and ashamed" and offered to support the Conservation department with education programmes or donations, but diversion was refused.

Newell said all forms of fishing were prohibited in the reserve. She said the pair were on a 6-metre boat at Dyke Head, well within the reserve on December 5, intending to collect seafood for an office break-up party.

At 10.10am, a fisheries officer found the vessel anchored about 500m inside the reserve boundary. The officer found them with nine crayfish in a bin, three of which were undersized. The men said they had not yet measured their catch and would have returned the undersized crayfish to the sea.

DOC seized their diving gear, but agreed to return it rather than seek forfeiture.

The hearing over a discharge without conviction will take place on November 23.