There are various ways animals in the sea can try to prevent themselves being eaten. Disguise, camouflage and speed are all methods employed by certain species. Using a hard shell is another common technique and this gallery shows examples of creatures that have evolved this way. For instance some live all their lives in a shell which grows with them. Others, like crabs, have shells but they need to change them periodically as they grow at which point they become very vulnerable to predation. Some crabs have only rudimentary armour and also use the ploy of disguise as well – see the Long-legged Spider Crab. The hermit crab is different and uses an empty shell of another animal as its home but again, as it grows, it has to find a larger one with the attendant dangers this entails.