They reckon if you farm the Hikurangi Swamp you know what to expect.

But four marlin turning up in this week's floodwaters, that's definitely unexpected.

If you farm the swamp, the soil is rich, the paddocks are flat - it is a place of bounty, with a catch.

Mother Nature occasionally ruins things for dairy farmers by flooding the place.

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Read more: Dumped marlin found on flooded Hikurangi Swamp farm

The flooding is controversial - farmers argue over how the floodwaters are diverted across the 5600ha of farmland.

Some perceive they take a more severe hit than others, and therefore experience more damage, more cost.

There are more than 60km of stop banks and several pump stations that work to mitigate the damage flooding can cause when the three rivers that feed into the head of the swamp swell with rain.

But even farmer Geoff Crawford must have been surprised during the latest bout of flooding, when four dead marlin floated in.

An eel or two, sure. But marlin are a rare find on the swamp. Their beaks had been removed, but the bodies were intact.

Either someone was about to prepare them for smoking, and somehow they "escaped", or they were dumped.

As Crawford, a former Northland rugby representative, says: "What does it take for people to dig a hole and bury them?"

It's a good point - if they were dumped then the laziness and idiocy of the act will only darken the already dim view many hold of big game fishing.