The problem, he said, was so bad that the regional harbourmaster Jim Lyle recently issued a directive banning anchoring in part of the Bay of Islands when larger vessels were moving within the harbour.
Mr Surendran said in many cases, people were so busy fishing from smaller boats that they did not even realise a large ship bearing down.
Since large ships visiting Northland weighed tens of thousands of tonnes and were about as long as Auckland's Sky Tower, they were obviously nowhere near as manoeuvrable as much smaller craft, he said.
"Not only are these big ships limited by their very deep drafts and unable to take evasive action easily, small vessels can also completely disappear from view under a larger ship's bow from as far as 200m away," Mr Surendran said.
He says Mr Lyle's directive applied to all vessels in the Bay of Islands Harbour, which was inside the line between Cape Wiwiki, Ninepin Island and Cape Brett, when larger ships were either approaching to pick up a regional council pilot, approaching to drop anchor or picking up anchor to leave the harbour.
This bans any vessel from anchoring within any sector of the Waitangi Sector light, from the 10m depth contour line adjacent to Hermione Rock, out to three nautical miles from Tapeka Point towards Ninepin Island when a vessel over 500 gross tonnes is moving within the harbour.
Mr Surendran said if a cruise ship was spotted, smaller vessels should immediately pick up anchor and move away from the limits of the sector light.
Meanwhile, he said in Whangarei Harbour, a permanent prohibited area also existed for safety reasons around the Marsden Pt oil refinery berths and access to an area around the nearby Northport wharf may also be off limits from time to time.
"As well as keeping an eye out for other vessels and staying out of prohibited areas, boaties also needed to steer clear of places where anchoring may be banned due to underwater cables or other dangers." he said.
Mr Surendran said a raft of information was available for those heading out to the water on www.nrc.govt.nz/onthewater.