The Torea is proving to be one of the toughest salvage efforts for a New Zealand company.
The Torea, with 23 people aboard, hit a rock and started taking on water before its skipper was able to run it aground near Ruapuke Island on Friday afternoon.
New Zealand Diving and Salvage has been working with local service vessels to lift the 20 tonne vessel.
However, NZDS director Dougal Fergus said soft sand and the age of the Torea were creating problems for salvage efforts.
''The vessel was in the worst water depth for operating lift bags,'' he said.
''The depth is too shallow to set up the lift bags for use at their full potential and not shallow enough to be able to seal the vessel and pump out the water.''
Salvage lift bags and pumps were sent from Wellington and arrived at the scene on Sunday, he said.
A 20 tonne of lift was applied to the vessel by the salvage team to try to stand it upright, but this amount proved to be inadequate, with extra lift required, he said.
Extra divers arrived yesterday to assist with putting another 20 tonne of lift under the vessel.
One of the issues is that the vessel has settled into the soft sand, making it extremely difficult to place lift bags under the hull, Mr Fergus said.
The age of the vessel and many deck openings was making it difficult for the dive team to seal the hull to make the vessel water tight, he said.
Pollution response gear remains on site and ready in case of any unexpected leaks.
Favourable weather conditions in the next few days was expected to allow work to be successfully completed, Mr Fergus said.
- © Fairfax NZ News