Zadar IV was the fourth planet in the Zader planetary system. Zadar IV had an ocean that was filled with dolphins and other marine life.
In the 24th century, Starfleet oceanographer Lieutenant Harry Bernard, Sr. was stationed on Zadar IV with his son Harry Jr. They lived on the beach and Harry Jr. often saw dolphins playing in the ocean there. They were later the inspiration for his first attempt at sculpting. (TNG: "When The Bough Breaks")
According to the Star Trek: Star Charts ("United Federation of Planets I"), in 2378, Zadar IV was a Federation member.