To a family visiting the seaside, a rock pool is a source of pleasure, but to the little creatures living in the water it is a harsh and dangerous environment.
"A rock pool is a nasty place to live," Gordon Croft of the St Andrews Sea Life Centre tells a group of schoolchildren. "The water gets warm in the sunshine, so it holds less oxygen for the animals to breathe. Then when the tide comes in the temperature drops suddenly and, unless you're stuck firmly on to something, the first wave picks you up and bashes you against a rock."
Which is why rock-pool residents often have protective shells and stoical natures. Some animals would resent being taken to school and handled by curious kids, but the starfish, mussels and crabs in Mr Croft's portable touch-pool remain unperturbed.
"Do you want to hold this starfish?" he asks. "He's supposed to have five arms, but he only has four because he has lost one. It's just beginning to grow back.
"Under his arms you can see all these tiny feet with suckers on, which a starfish uses for moving around and feeding. It wraps its arms around a mussel and sticks on. Then it pulls the shell open, pushes its stomach out of its mouth and around the mussel, and turns it into a sort of soup." At this point the appeal of holding the starfish seems to wane, and it is hastily unwrapped from little fingers and returned to the water.
Other contents of the touch-pool include whelks, sea-urchins, baleen from a piked whale's mouth and the tooth of a sperm whale, once used to seize and eat giant squid a mile under the ocean. But the most dangerous animal of all, says Mr Croft, is a human, whose plastic litter can remain in the sea, and will trap fish and small animals, for 500 years.
"I adapt the talk, depending on the kind of feedback I get and the age of the children," he explains later. "Some of them have never been to a beach, while others are really clued-up.
The ideal age is probably Primary 4 to 7, when they're old enough to understand but don't mind if they say the wrong thing, so you can have fun with them. Often they'll come to the centre long afterwards and remind me what I told them. Young kids absorb a lot more than you'd think. They're like wee sponges."
To book a session with the touch-pool between now and March 19, phone the Science Festival box office, Tel: 0131 473 2070. At other times, or to arrange a school visit to the St Andrews Sea Life Centre, tel: 01334 474786