Two sharks more than seven metres long were spotted off the coast of Soller last week, but although it is one of the biggest creatures to be found in the Mediterranean, it is inoffensive. Shark expert Juan Poyatos said that last weekend, the waters off the island were very clear and calm, and many people out sailing were able to observe the sharks. This particular species, he says, feeds on micro organisms. It is not unusual to see them off the coast in winter, as they usually come in search of warmer waters. He advised sailors not to go too close in order not to alarm them. But, Poyatos said, their worst enemy was not man but plastic bags. Sharks have been around for 400 million years or more and have survived in crystal clear waters. But the proliferation of plastic and other rubbish dumped at sea by humans is playing havoc with them. A pair of sharks, possibly the same two, was spotted in the port of Mahon earlier this week. The peregrine shark, which takes its name from its long migrations, is characterised by swimming with its mouth open. It nearly always swims on or near the surface and nearly always travels in pairs. It is one of the species of shark which is in danger of extinction. Last summer, the Playa de Palma was closed for a few hours on two separate occasions when there were reports of a blue shark swimming near the coast. The sightings then were not confirmed and a search by helicopter did not spot the shark.