Blue sharks migrate UK waters in the summer, following their food.
It is hoped the footage from the Inner Hebrides will reinforce a case for conservation in the area.
Two sharks weighing more than 500lbs have been caught seven miles off Portland in Dorset.
These sharks thought it was swordfish on the menu, but there was something hungrier in the darkness.
BBC News Online
More than 1,000 sharks and rays have become entangled in plastic debris in the world's oceans, according to scientists at the University of Exeter.
They say the true number is likely to be far higher, as few studies have focused on plastic entanglement among shark and rays specifically.
They're now calling for a "citizen science platform" to be set up online or on smartphones to help crowdsource reports.
The study found such entanglement – mostly involving lost or discarded fishing gear – is a "far lesser threat" to sharks and rays than commercial fishing, but the suffering it causes is a major animal welfare concern.
"The shark had clearly continued growing after becoming entangled, so the rope – which was covered in barnacles – had dug into its skin and damaged its spine," he said.
"Although we don’t think entanglement is a major threat to the future of sharks and rays, it’s important to understand the range of threats facing these species, which are among the most threatened in the oceans."