The Hawke's Bay Regional Council says it will no longer let boat owners off with a warning if they pass too close to ships in Napier.
The council is concerned about an increase in near misses and will now prosecute skippers who put themselves in danger.
Boaties must stay more than 500 metres from a ship's bow when crossing its path.
Council spokesperson Bryce Lawrence says in one recent case a small boat passed so close to the bow of a cruise ship that the master of the ship lost sight of it.
The skipper of that boat is being prosecuted.
Mr Lawrence says it's unfortunate it's got to this point, but says the action will create awareness about the rules.
He is reminding boaties to always take time to navigate around ships, and keep at least 100 metres from their side or stern.
Mr Lawrence says skippers who are prosecuted could be fined thousands of dollars and lose their operator's licenses.