AN EYEWITNESS of an ongoing incident on the Clyde says they thought the terrifying ordeal was a 'training exercise'.

A major emergency rescue operation is under way after a boat sank off East India Harbour in Greenock.

An eyewitness, who arrived on the harbourside shortly after the incident started to unfold, said: "When we arrived, we thought it was a training exercise.

"It looked like the rusted hulk of a wee boat or something.

READ MOREMajor emergency as boat sinks in Clyde off Greenock

"We were busy looking at the Hebridean Princess, I thought it must’ve been a training exercise.

"I didn’t realise there was anything untoward until the other boats started coming.

"Someone from the boats that arrived got on top and was tapping and shouting on the hull asking if there was anyone in there.

"All of a sudden it was a hive of everything, there were boats and helicopters. I just hope they’re alright."