Not sick, necessarily, but definitely very overwhelmed. They'll be a bit more sluggish in the warmer waters, and stick to the darker, shadowy areas to have the best chance at fighting back. They will also be stealing a lot of food to keep their energy up -- they definitely don't look Great, and some of them (while determined to fight) will definitely be focused on trying to feed themselves in order to keep going.

They are actual monsters of the rift! Beasties with a lot of gnashing teeth. However, dreamscapes can wield whatever your character's imagination can summon up -- those are not real. But the rift monsters are very much real, and can and will kill you if you let your guard down.