We don’t necessarily need a Loch Ness monster boss but it would be cool if we did because Minecraft needs more boss variety. It would spawn in a special lake biome and it would attack by using its neck as its main attack and a head bash as a secondary attack that would do more damage. It could have less health than the wither or more depending on how Mojang would balance it. And finally it would drop scales to make an armor stronger than diamond and possibly it would drop it’s teeth which can be crafted with scales to make an underwater elytra.
was there another alternative to "Mob B" /the Phantom of the 1.13 Aquatic Update Aquatic (the Phantom of the Aquatic), that would drag Players down, into Water? Other than the "Blaze Boss," I mean, and there was a 4th too even voted-upon then.
All I know's the latest pseudo-headline is "the 'Real Life' 'one'"( ..? question mark as in, "was it /were they Ever, 'real' ?!?" A. : quite-possibly not) "could be a 'giant eel'." Before that the same sources had multiples "'claiming' 'plesiosaurs'" (extinct since Dinosaurs-too).
Anyway, I think this Water one I'm remembering also was said to have a longer part and /or shoot something (like Octopods) into the Water (like the-New, Ink-reaction, Squirted), to obscure it (from being counter-attacked? or just to hide it??). I really like your: "like 'underwater Elytra'," idea, though; Phantoms already look like "manta rays" of course, including down-there.
If there were a less-deadly (and let's face it: Phantoms are Difficult-enough to counter-attack that they're more-dangerous than the Player, on average; we have to use luck to damage them, but they basically almost-always hit /bite us) "gliding" / "swooping" UnderWater Mob - which could include the Player, the Player's considered a (unique, but still) Mob (see: Animal; in Reality, too [regarding humans, and no, I don't mean sometime "Humans," in-Game]) - it'd be the next-thing to a Dolphin, et. al. (since no "sharks," or-whatever). I dunno, some kind of "(water) jet propulsion," and /or "slippery-slidy scaly" thing (hagfish and /or lampreys use "super-lube," for everything), you're talking about.