The operation is underway to submerge the capsized tourist boat in Akaroa Harbour

The Black Cat Cruise vessel was carrying 38 passengers and three crew when it ran into trouble on Saturday afternoon - all were safely rescued.

Environment Canterbury says more than two-thousand litres of marine diesel fuel has been released to the sea, but the environment appears to be coping with the spillage.

Phase One of the recovery operation involves moving the vessel into deeper water to prevent further structural damage from wind and sea conditions.

On Scene Commander Emma Parr says environmental monitoring is continuing and wildlife response specialists remain on standby.