Grebes are small to medium-sized, long-necked near-exclusively aquatic birds. Thye have distinct breeding and non-breeding plumages. Their legs are set far back on the body, therefore they can only difficultly stand and move on land. They ahve long, slender necks
They occur mostly in freshwater wetlands, but some also frequent saline pans and coastal marine waters.
They are superb divers and the actively pursuit pery under water. They mainly eat fish, frogs, tadpoles, crustaceans, mollusks and aquatic insects under water. Grebes swallow their own body feathers and feed them to their young, possibly to assist in pellet formation.
Their nests are floating mounds of damp aquatic vegetation, They lay 2 - 5 eggs. On leaving the nest, adults cover the eggs with nest material. Incubation and taking care of the chicks is done by both sexes. The chicks are fed solid food, bill to bill. Young chick are often carried on the backs of the swimming parents. During moult all flight feathers are droppen simultaniously, leaving grebes flightless for 3 - 4 weeks (little grebe might be an exce;lption in this).

Tachybaptus = fast diver

Wikipedia

fatbirder.com