Battle for the Golden Sun (1988)

A navigational accident has led the Empire to the mysterious and legendary water world of Sedri. Rebel spy networks carry troubling tales back to Alliance High Command, rumors that Sedri holds the secret of the Golden Sun - a secret thet could give the Empire the Power to crush the rebellion once and for all!
An alliance dignitary, young and impetuous, disappeared while checking into these disturbing rumors. Now a special team of Rebel agents volunteer to undertake a desperate mission. Guided by a half-sane Mon Calamari, they must make their way to Sedri, locate the missing dignitary, avoid imperial entanglements, and solve the mystery of the Golden Sun.
If the rumors prove even partially true, then this band of Rebels is all that stands between the Empire and total control of the Galaxy...