Four students from Oxford were spurred on by an inquisitive pod of dolphins as they swam from Europe to Africa.

The quartet became the second group of students from the city to cross the Gibraltar Strait between Spain and Morocco this summer when they completed the feat last week.

Having weaved across busy shipping lanes, dodged sharks and battled strong currents, the group came ashore to collect £6,160 in sponsorship for the World Cancer Research Fund (WCRF).

Emma Penn, a 21-year-old chemistry student at St John's College, swam the entire 22km route, while Ginger Turner, 25, James Briaris, 26, and Darek Nehrebecki took part in relay.

Friends Nate Singer, 25, and Nicholas Staubach, 25, also completed the marathon.

Miss Penn's time of 4hrs 35mins was a minute quicker than that of celebrity duo David Walliams and James Cracknell, who took on the challenge in March, and just under an hour slower than the British record set by fellow Oxford University students Lennard Lee, Harry Fisher and Nicholas Berry in July.

She said: "It's only just sinking in now that I managed to swim it all. It was really hard — the water was so salty and cold.

"The last kilometre was the worst, it felt like the shore kept moving away from me.

"But it was worth it for such an incredible exper- ience.

"The most amazing bit was when dolphins came circling around me.

"I could see their fins and hear them squeaking in the water. It was then that I realised I was in the middle of the ocean.

"I couldn't see anyone or anything apart from the dolphins.

It was an amazing moment, but terrifying.

"We decided to raise money for the WCRF because we have all lost relatives to cancer. It is something that affects everyone and the more research that can be done into cancer prevention the better."