However, the sixth chapter of Genesis reveals some often overlooked, but very important details. For example, the Bible nowhere states Noah had to take on board representatives of every living creature. There were three requirements for the animals to be loaded on the ark. They had to be:

• Air-breathing.
• Terrestrial (land-dwelling).
• Of the same biblical kind.

The ark did not need to carry every species (possibly numbering in the millions) of animal. It was designed to carry only every biblical kind (numbering in the few thousands) of terrestrial, air-breathing animals. (Genesis 6:17-20). (For further information, see “Understanding Biblical ‘Kinds. ‘”)

Also certain animals  would have survived the Flood without an ark. These would have included aquatic animals such as the crustaceans (lobsters, crab, etc.), salt and freshwater fishes, echinoderms (starfish, sea urchins), mollusks, worms, corals, sponges and myriads of other specimens of animal life that do not live on dry land.

This  would have also included such mammals as the whales, porpoises, seals, walruses and others that live in aquatic environments even though they breathe air. Some reptiles and most amphibians would also fall into this category. Many other animals that are terrestrial may have also been able to survive outside the ark, such as insects and protozoans. 
God reiterates this point when He describes the kind of animals that perished during the Flood. These were specifically the type of animals that Noah was told to take on board the ark. “Every living thing that moved on the earth perished—birds, livestock, wild animals, all the creatures that swarm over the earth, and all mankind. Everything on dry land that had the breath of life in its nostrils died” (Genesis 7:21-22, New International Version, emphasis added throughout).

Size of the ark
Another major misconception concerns the size of the ark. It was an immense ship. By comparing the measurements of the ark, it is easy to see it would be comparable to today’s oceangoing vessels. It was probably the largest vessel of its type built until the late 1800s when metal ships were first constructed (see John Whitcomb and Henry Morris, The Genesis Flood , 1998, p. 10).

Caring for the animals
Many scoffers regarding the Genesis Flood state it would have been impossible for the eight-person crew of the ark to have adequately cared for all the animals. The ark likely made use of self-feeding, self-watering and self-cleaning technologies. Such labour-saving designs were fairly common knowledge in the ancient world.

Nature of animals a factor
It is also possible many animals, which are not considered classic hibernators, have the latent ability to greatly lower their metabolic rates (Terry Vaughan, Mammalogy , 1986, pp. 421, 469-471). Such lowered metabolic rates can be brought on by several factors including temperature fluctuations, unavailability of food and water, variability of light and other environmental stimuli.
When all the facts are considered, the crew of the ark could have cared for thousands of animals. Data from animal husbandry studies have shown a few people can care for tens of thousands of animals (John Owen, Cattle Feeding , 1983, p. 101; E.C. Miller and E.F. Hodges, “One Man Feeds 5,000 Cattle or 60,000 Broilers,” 1970 Yearbook of Agriculture (USA), p. 57).