How come after the great carp dies, it ends up in the apes watering hole, but not the bottom of the lake in fountainhead palace like the rest of the skeletons there?
So the way the Lotus of the Palace and other Sunken Valley related item descriptions make it seem is that the Sunken Valley is a collecting point for the Fountainhead waters. This is just my theory, but maybe there's basically a magic water portal connecting the two locations, and the great colored carp somehow went through it. Not a great explanation, but it's all I can think of.