Endurance athlete Diana Nyad has had to abandon her historic attempt to swim between Cuba and Florida, after encountering stormy weather, shark threats and jellyfish stings.

A post on her blog states that she realised that "the obstacles against the swim were too great", and that she agreed to abort the swim "for the safety of her team and herself".

Nyad was stung nine times by jellyfish on Monday alone, and after swimming into a storm 55 miles off the coast of Key West, her support team had to pull her from the water. Despite suffering swollen lips and hypothermia, Nyad initially wanted to return to the water. However, after listening to her support team, she eventually agreed to return to Key West by boat.

The journey hadn't been all bad. In this footage filmed yesterday by Gunnar Schrade, a pod of dolphins visited Diana and began swimming by her.

Nyad, who turns 63 on Wednesday, was attempting to become the first person to cross the 103-mile Florida straits without a shark cage. This was her fourth attempt at the marathon swim, but each has ended in failure.

Only one person has ever managed to swim the crossing with the help of a shark cage, Australian Susie Maroney, in 1997.

Written and presented by Alfred Joyner