Conan the Barbarian #98 (Marvel Comics, 1979)

As Conan, Belit, and the crew of the Tigress sail on the Western Ocean, a fantastic sight is spotted in the distance! A beautiful woman with blue skin and green hair stands on a floating lily pad in the middle of the high seas.

Belit, on brand, is immediately jealous and suspicious of this nautical wench and calls her a "Sea-Witch", then suggests they sail past and let her drown.

After a shark nearly eats her, Conan and the crew rescue her, against Belit's wishes.

Belit was right about this one, of course, because the strange girl is mute and acts suspiciously after they loot a Stygian vessel. She flirts with the crew and even tries to seduce Conan, who barely escapes without a kiss. Some of the other crew members are not so disciplined, however, and fall victim to this mystery-woman's silent song.

One by one, the crew goes missing. She dives into the ocean and lures a man out to save her, then kisses him. Moments later, the man drowns and dies.

Conan, watching from the boat, catches on at this point, but before he can skewer her with a spear, he falls victim to her song and dives into the water. His head clouded with visions, Conan swims out to greet her with a knife, but she thrusts a kiss upon his lips and sends him into a dream state of visions.

Belit rushes onto the deck and calls out to Conan, pulling him out of his trance. In a rare moment of weakness, Conan struggles against this formidable blue foe and nearly drowns. Her strange magic prevents him from stabbing her, yet as Belit continues to call his name, Conan drags her to the Tigress and then pulls her on board... only to discover that she is actually seaweed!

Conan and Belit embrace. It is their love that saved them from the weird seaweed sea-woman from the sea.