A group opposed to seabed mining has sent out boats to protest against seismic testing it says is being carried out in a dolphin sanctuary off the west coast of the North Island.
Group member Phil McCabe says Kea Petroleum is conducting sonic booming from the MV Voyager Explorer in a sanctuary for Maui and Hector's Dolphins.
The technique involves using airguns to create an extremely loud pulse of sound to map the seabed.
Scientists say there is evidence this may disrupt or damage whales and dolphins and has been linked to strandings in other countries.
Mr McCabe says two boatloads of protesters took to sea off Taranaki on Thursday and stayed a short time near the Voyager Explorer hanging out banners and taking photos.
The Department of Conservation says the surveys can be carried out in a sanctuary area, so long as regulations are followed.
DoC says a voluntary code of conduct developed by the department and the industry minimises impacts.