Kim went into selfie mode, posting a shot of herself laying out in a brown two-piece, and included the caption, "Sweet sweet fantasy baby."

We're sure Pete will co-sign on that -- as we've told you, the couple arrived in the Bahamas yesterday via a private jet and boat ... and they were all smiles as they touched down.

So far, they're enjoying some good vibes and relaxation, despite their trip coming just as Kim's ex-hubby, Kanye West, has been on a string of dates with actress Julia Fox -- they were all over Miami last weekend, before hitting NYC for dinner, at Carbone, and a Broadway play.

It's hard to ignore Kim and Julia might have the same taste (literally) -- Carbone is Kim K's fave restaurant and Julia's been decked out in Balenciaga ... which has become Kim's signature over the last year. 🤔

If the jury's still out on whether Ye and Julia are a true romance or just-for-show-mance ... Kim and Pete have definitely gotten more serious. Remember, a few weeks ago, they rented out a movie theater to watch "House of Gucci"... and this was no ordinary theater. It was the Staten Island cinema Pete's been going to his whole life.