In Porthcawl, the volunteers of the RNLI race to save a surfer at the mercy of Storm Brendan. Meanwhile, in Selsey, a family's day out for a spot of paddleboarding goes badly awry when the father becomes separated from his young children, leaving them stranded on a rapidly dwindling sandbank.

The volunteers of the RNLI battle to save a mother and her son who are caught in a rip current, plus a man who has fallen over 100 feet from the top of a cliff.

The lifeboat volunteers pluck a fallen climber out of the sea in Wales and is within seconds of falling unconscious. Meanwhile in Scotland, a team rescue a 170-ton fishing boat that is perilously close to the rocks in gale force winds, and in Minehead, three kayakers are swept out to sea as darkness falls.

The crew at Tower, on the River Thames in London, is the busiest of all the lifeboat stations, averaging more than 500 shouts a year and aiming to launch to any emergency in under 90 seconds. When a call comes in about a man in the water near the Thames Barrier, they reach him with just moments to spare. In Fleetwood, on the Lancashire coast, a desperate 999 call alerts the crew to a bait digger - out looking for worms on the sand flats - who has been caught out by the incoming spring tide and is in danger of being submerged and swept out to sea.

In Trearddur Bay, the RNLI crew battle through gale force winds and huge waves as they try to save a surfer, as their worried families watch on from the shore. On the same stretch of Welsh coast, the Llandudno and Rhyl lifeboats are involved in a desperate search for a fishing vessel that's reported missing.

In St Agnes, the crew is involved in a race against time to rescue two young men. They are reported to be struggling in the water near a notorious headland known as Tubby's Head. In Whitby, North Yorkshire, Leah is training to be the station's first female helm, and her skills are put to the test when she is called out to rescue a walker who's fallen and injured her leg on inaccessible rocks by the seal colony at Ravenscar.

Whenever the crew’s pager sounds, they know they must prepare for all eventualities. At Beachy Head, the Eastbourne crew have to deal with a base jumper’s disastrous takeoff. Just along the Sussex coast in Newhaven, a man faces a race against time as he suffers a seizure on board a tall ship. At Loch Ness, a World War II sea plane runs into mechanical trouble. And in Rhyl, a dog chasing seagulls into the sea bites off more than she can chew.

On Ireland's south-east coast, the three RNLI crews at Dunmore East, Kilmore Quay and Rosslare battle to save a cargo ship that has lost all power and is drifting towards rocks. In Hoylake, on the Wirral, a vast multi-agency effort is required to rescue a mother and daughter who have got stuck in the mud and, 65 miles to the west, in the coastal village of Porthdinllaen, the crew respond to a mayday call from a yacht five miles out in the Irish Sea that is requesting an immediate medical evacuation.

Just off the west coast of Scotland, on the rugged Isle of Mull, the Tobermory lifeboat crew have to battle huge waves to save a 40-foot fishing boat that has lost all power.

In Portrush, Co Antrim, the crew race to rescue a boy who has got into difficulties after jumping off rocks, and one of the crew volunteers enters the water to save him. On the Pembrokeshire coast, the lifeguard team at Whitesands Beach join forces with the St David lifeboat crew to rescue someone who has been found unconscious in the water