A passenger vessel carrying 41 people began taking on water after striking a submerged rock near the entrance to Akaroa Harbour, with crew later struggling to operate one of its bilge pumping systems, an interim investigation report has found.

The Transport Accident Investigation Commission has released its interim factual report into the grounding of the Black Cat on 31 January.

The 17 metre catamaran, operated by Black Cat Cruises, was carrying 38 passengers and three crew on a scenic cruise when the incident happened.

The Commission said the weather was calm as the vessel approached Archway Rock after visiting Scenery Nook.

Shortly before the impact, one crew member saw the Black Cat approaching Archway Rock from what they considered an unusual direction and went to the bridge to raise their concern with the master.

Seconds later, passengers and crew felt a bump and heard a scraping sound.

Location information recovered from photographs taken immediately before the impact, along with data from a GPS tracker on the vessel, placed the Black Cat over a charted submerged rock where the depth was unknown.

The master initially thought the vessel may have struck the float of a crayfishing pot.

About a minute later, a bilge alarm sounded.

The master checked the starboard engine room and found seawater had entered the compartment, with the water level around the top of the engine.

The report said the vessel’s starboard hull had been ruptured.

As the Black Cat headed back towards Akaroa Harbour, its steering stopped working, along with its CCTV and public address systems.

The starboard engine and propulsion system also stopped operating, while the emergency steering system did not respond.

The master instructed two crew members to start an engine driven bilge pump.

However, the Commission said the crew were not confident about how to operate the system and the pump was not started.

The Black Cat was equipped with four separate bilge pumping systems.

Passengers were told to put on lifejackets as smoke or steam began entering the main cabin and the vessel developed a significant list to its starboard side.

Several nearby boats responded after the master radioed for assistance.

At about 12.32pm the master broadcast a Pan Pan urgency call, advising that the Black Cat was taking on water.

Passengers were then moved towards the port side of the vessel and evacuated onto assisting boats.

All 38 passengers and one crew member were safely off the Black Cat by about 12.40pm.

The master and another crew member remained on board as an attempt was made to get the vessel towards the beach at Nikau Palm Gully.

Coastguard personnel also boarded with a portable water pump and attempted to remove water from the vessel.

But as the Black Cat settled lower in the water, seawater began flowing onto the aft deck and those remaining on board began evacuating.

At about 12.47pm, the vessel grounded while approaching the beach.

The master shut down the remaining engine and left the Black Cat on a jet ski which had been standing by.

No passengers or crew were injured.

Environment Canterbury declared a regional oil spill response later that afternoon.

Attempts to refloat and recover the Black Cat were unsuccessful and the vessel later broke apart during heavy weather.

The Commission said all vessel debris that could be safely collected had been recovered by 19 March and Environment Canterbury reported the environmental impact was minimal.

The Black Cat was built in Australia in 1994 and had operated from Akaroa since 2004.

The Commission said its investigation remained underway.

The interim report contains factual information gathered so far and does not make final findings about the cause of the accident.