The answer is - Sponge.
Sponges are very lightweight, they have large percentage of voids as well, this practically means that they have low density structure. Their density is smaller than the density of the water, so this means that it will float on the water instead of sinking.
Answer:
Humans need certain resources to survive at subsistence level -- most commonly air, food, water and usually some kind of shelter. A sustainable habitat is one in which supply of and demand for these resources are balanced.
