Pesca was a planet in the constellation of Pisces. Covered with vast oceans for thousands of years, its orbit brought it closer to its sun so that its seas began to dry up and all marine life began to die.
By the time the Fourth Doctor arrived at Pesca in the 15th century, the surface of Pesca was a vast wilderness. Zor, leader of the native Pescatons, had brought him to the dying world to help them find a new planet. The Doctor refused, defeated Zor in mental combat, and escaped back to the TARDIS.