Yeah, we should be getting it. As far as I can tell, there were two quests to fight. An easy one where you fight urukusuru and a hard one where you fight Jinouga. I think these might be the quests you fight in the demo, but I may be wrong. They may have the Plesioth in underwater battle for a demo as well since it was in the Japanese one.
3DS FC: 3136 - 7465 - 9458 The official name is Jinouga. Screw what Capcom says, its Jinouga.