Beginning tonight, ABC wants us to sail away on "The Love Boat" to "Fantasy Island" every Saturday night.

Watch out for seasickness and jungle fever.

You may already have a nodding acquaintance with "Fantasy Island" (and we do mean nodding). Two feature-length pilots have been broadcast, including one last Friday, Fantasy Island is a little spot in the tropics where Ricardo Montalban makes dreams come true.

Every week "Fantasy Island" will bring us the enactments of two guest characters' fantasies. The stories converge much as they do on "The Love Boat," and the two shows share executive producer Aaron Spelling. It's probably no accident that the time slot "Fantasy Island" fills, an hour at 10 p.m., was vacated recently as "The Love Boat" moved up an hour to 9. "The Love Boat" is a hit, and "Fantasy Island" is the residue.

A thin fantasy this is. We learn quickly that everything will always turn out right, and the scripts insert willy-nilly doses of would-be warm-hearted sentiment. The Montalban character is not beyond behaving like a sadist and liar, so omnipotent is he in his little kingdom, but naturally father always knows best. He was just kidding, we learn. And down deep, he's a real man of the people - he charges his customers only what they canafford.

"Fantasy Island" lacks even the comic grace of "The Love Boat." Little Herve Villechaize, as Montalban's Friday, is the source of most of the comic relief, and his jokes wear thin. "Fantasy" alternates romance with adventure in a perky, schematic fashion that seems straight off an assembly line.