The sight of a dorsal fin cutting the water is a great excitement on a seaside trip, but whales and dolphins are at risk in the holiday season.

Conservation experts are warning that the animals, including the minke whales spotted by fishermen in Swanage Bay last week, can be disturbed or harmed by more people being out on the water.

"There have been a few really sad incidents in Swanage last year," said Ali Tuckey, assistant ranger at Durlston Marine Project.

"We had a pod of dolphins in the bay which were instantly surrounded by 10-15 boats heading straight into the pod.

"A lot of noise from different directions confuses their echo location and they can strand themselves or panic or potentially get injured by running into a propeller or boat."

Because of the increased boat traffic, bottlenose dolphins tend not to get too close to the coast in summer but there are dangers posed to and by lone mammals which do seek out human company.

For over six months four years ago, George the friendly male bottlenose dolphin delighted swimmers along the Dorset coast.

"There were a few incidents of people putting their kids on his back and he could have accidentally injured someone," said Ali.

In fact several people were bitten, hit by his tail or butted and one was tossed out of the water and had to be treated in hospital for shock.

"They are wild animals. Let them come to you rather than approaching them.

"It's all about showing respect for them really," she added.

And that is the message from the Whale and Dolphin Conservation Society, which is urging all boat owners to follow its code of conduct when on the water.

"We are asking boat users, please do not chase them and to be very careful when manoeuvring if these animals are nearby," said Mark Simmonds, director of science. "Even friendly dolphins can become frustrated, frightened or angry and these large and powerful animals are quite capable of hurting us, just as we are capable of hurting them."