Retired Navy Commodore Peter Scott discusses the reason why finding the Titan submersible is a difficult task.
"There's a lot of things making this a very difficult search and rescue operation," Mr Scott told Sky News host Sharri Markson.
"To start with it's several hundred miles off the Canadian coast, so any search vessel whether it's air or sea needs to be mobilised and needs to get there; that can take days as we've seen."
"You've got to have the right technology" and equipment because it has to be able to get down to a depth of almost 4000 metres, Mr Scott said.
"So, very difficult circumstance."