An old doodle based on Classic Maya depictions of fish. To my knowledge, there are two major roles that fish play in Classic Maya art. The first is more pictorial, showing them nibbling on things or otherwise swimming about, to indicate that a scene is underwater, or that the figure they're associated with is associated with water (or the watery underworld.) The second is in writing– either as the logogram KAY, standing for the word kay (fish), or as the syllable ka. You see a lot of the latter in the word cacao, where the syllabic duplication symbol is cleverly placed as bubbles by the fish's mouth, rendering ka-ka instead of just ka. Add wa, which often resembles the fish's fin or tail, and you have the word ka-ka-wa – cacao. This is just off the top of my head, though– I can't say for sure the origin of the wa syllable or the full significance of water imagery to the Maya.