Maritime NZ is asking recreational sailors not to go into BoP waters for fear of dragging oil into cleaner areas.

Thieves have made off with anchors from a boom protecting an estuary from the Rena oil spill.

The crippled MV Rena could be a blot on the Bay of Plenty coastline well into next year if bad weather doesn't smash it apart and the cost of the clean-up and long salvage operation could stretch to $100 million.