Razorfish were a kind of aquatic mammal. Their primary defense were razor-sharp scales which lined their bodies. Brushing against a razorfish could result in a serious wound. They were found both in the sea around Metru Nui and the waters surrounding Mata Nui.1
Notes
Razorfish were mis-named and were actually aquatic mammals. Their body was lined with incredibly sharp scales. Merely brushing against a razorfish was enough to cause serious wounds. On Metru Nui, razorfish were known to make huge gashes accidentally in the sides of passing Matoran boats.2