Trist is a fictional Earth-sized planet orbiting Epsilon Eridani. Like Earth, it has large oceans, but the only life is in the oceans. The dominant life forms produce chlorine, making the atmosphere poisonous to humans. Colonists live in tunnels underground.

Epsilon Eridani

Epsilon Eridani is about twelve light years (about 72 trillion miles) from Earth, and about five light years from Tau Ceti.  Current data indicates the possibility of two planets.