The easiest thing to crochet. Crafty Scrappin Vintage patterns has if for sale, but visual crocheters should have not problem doing this. It is triple crocheted.
i think you could make this with tunisian. when it gets the the split, you could keep working half the stitches until both halves are long enough and then start stitching across the entire piece again at the other end.
Nica Tank by Sunday in Brooklyn (Anthropologie)