After a plane nearly sank Saturday morning while moored to a dock at Vancouver's float plane terminal in Coal Harbour, the plane's owner and the terminal's operator disagree on the cause.

At about 4:30 a.m. staff from the nearby Vancouver Convention Centre noticed the tail of a plane owned by Harbour Air was submerged halfway in the water. By 8:30 a.m. a crane was brought in to pull it out.

"We've got large concerns on the construction of these docks and the safety of these docks," Randy Wright of Harbour Air told CTV News.

Harbour Air stationed the plane at the terminal owned by Ledcor as a way of a testing its safety concerns.

"The ropes popped on the first night and then last night the air craft sunk," Wright said. He believes the plane's pontoon was rubbing off against the dock and then began to take on water.

Ledcor, the operator of the terminal, claims the pontoon was already damaged.

"The Harbour Air maintenance crews were regularly tending to this float, which indicates that there was knowledge that the float was taking on water," Ledcor spokesman Lee Coonfer told CTV News. "That maintenance, the last one, was done at 3 p.m. the day before."

Ledcor points to a surveillance video to back up its claims. The video shows the plane's tail dipping into the water around 3 a.m. followed by the right wing, which was located on the side away from the dock.

"There was no contact with the dock and that particular float. The plane was anchored to the dock by the left float," Coofner said.

Conflict over the terminal is nothing new. The $20-million facility was built to replace the existing, aging terminal, and plane operators were told to relocate when it opened in May.

But Harbour Air, the city's biggest float plane operator, refused to move citing increased costs and safety concerns

Ledcor insists its facility is safe and believes it actually saved the plane.

"This is a brand-new dock, cement structure, and the integrity of this structure saved the plane from going down," said Paul McElligott, Ledcor's president of resources and transportation.

An investigation into what caused the plane to sink is underway.

With a report from CTV British Columbia's Penny Daflos