As the water starts to warm in the summer, marine giants arrive at the Celtic deep. Some have travelled for thousands of miles to feast on plankton and abundant shoals of fish. Visitors include a group of fin whales. At 25 metres long, these majestic submarine-shaped creatures are the planet’s second largest animals. Joining them to hunt sardines are 2 metre long blue-finned tuna. These sensational super hunters have exciting courtship behaviour.