The party followed Monkey Kong’s lead and went looking for sick whales up north in their boat. They found them but couldn’t carry the whales, so Isaac jumped into the ocean. The synth piece of cloth that he carries with him started singing to the tune of the whales and attracting them.
They found a sickly one and followed her to shore where she died. There was metal in its mouth. They examined the beach and did find a reddish stream dumping into the ocean. Eventually they followed it to some pipes with some sort of industrial waste sludge. Following the general direction of that (it was buried underground) the found a ghost town with a sole survivor, he said the rest of inhabitants had been poisoned when the stream water turned red.
They looked at the map and found that the nearest settlement was upriver towards the capital.