While at the beach you will see many varities of sea-life.

Periwinkles, with snail-like shells. Found in and around the rock pools, everyone enjoys 'picking' periwinkles. These can be boiled and make an enjoyable, if salty, snack. Bring a container and collect some sea-water to boil them in, for about 10 minutes and use straight pins to eat your gourmet snack.
Limpet (or barnacles) , with arched, nonspiraling shells. Limpets are almost worldwide in distribution. These are commonly found clinging tenaciously to rocks or submerged timber. Limpets scrape out a region of rock as large and as thick as their shells, and return to this region at night for protection; during the day they move about in search of food. They subsist on marine vegetation, especially algae.
Limpets are used as food and as bait for fishing. A bit chewy for my liking but a popular snack.