Wazamaji (tafsiri kutoka Kiing.: diver) ni ndege wa maji wa jenasi Gavia, jenasi pekee ya familia Gaviidae. Wanafanana na vibisi na minandi lakini ni tofauti na wamepewa oda yao Gaviiformes. Wana ngozi kati ya vidole kama minandi lakini domo lao lina ncha kali bila kulabu kama vibisi. Kama zile spishi nyingine huzamia kabisa ili kukamata samaki, gegereka, amfibia, koa na luba. Hulijenga tago lao kwa matope, mimea ya maji na manyasi ardhini karibu na maji ya ziwa katika kande za kaskazini za Amerika, Ulaya na Asia. Jike huyataga mayai 1-3. Nje ya majira ya kuzaa hupatikana baharini na spishi kadhaa huhama mpaka pwani za Afrika ya Kaskazini-magharibi. Gavia arctica, Mzamaji Koo-jeusi (Black-throated Loon, Arctic Loon au Black-throated Diver) Gavia immer, Mzamaji wa Amerika (Great Northern Loon, Common Loon au Great Northern Diver) Gavia stellata, Mzamaji Koo-jekundu (Red-throated Loon au Red-throated Diver) Gavia adamsii (Yellow-billed Loon au White-billed Diver) Gavia pacifica (Pacific Loon au Pacific Diver) – zamani katika G. arctica) Mzamaji koo-jeusi Mzamaji wa Amerika Mzamaji koo-jekundu White-billed diver Pacific diver