Great pond snails have lungs and need to surface regularly and take a breath. They eat just about anything they run into, even their own excrement. That sounds disgusting, but it means that they only waste 15% of what they eat. A pig wastes 6 times as much with its excrement! Pond snails are both male and female simultaneously and mate with another snail or with itself. The chains of eggs are attached to the underside of drifting leaves. After 10 days, the small snails hatch.