Dr Simon Berrow of the Irish Whale and Dolphin Group and Dr Mauvis A Gore of the Save our Seas Foundation spent three days being filmed tagging the docile sharks - the second largest fish in the world - to help trace their movements. They were guided by Inishowen Wildlife Service Ranger Emmett Johnston.

Crossing the Line Film Production Company funded the pilot project, which is due to be a premier feature in a three-part flagship production for RTE about wildlife migrations.

The film crew operated out of Culdaff with skipper Des Mills on the Gemini II and with the assistance of Lough Swilly Sea Safari.

They captured the exciting scenes at Inishtrahull Sound as the scientists tagged six basking sharks - the most ever tagged in Irish waters.

Emmett Johnston said: “Inishtrahull Sound is fast becoming a international hot spot for the Sharks and we want to positively promote the area as a place to conduct marine research.

“This is a fantastic natural resource we have on our doorstep.

“The fact Crossing the Line Productions flew in experts from Scotland and a film crew from France just for these three days is testament to the special nature of this resource.

“Nowhere else in the North Eastern Atlantic is getting such regular Basking Shark numbers this late in the season.”

The team placed red visual identification tags on the sharks and plans to return next May to place satellite tags to help track the huge fish.

Mr Johnston added: “Extremely little is known about basking shark ecology, as they are the most under-studied mega-fauna species on the planet.”