Fire ants like many species of ants make their homes underground. They are composed of a complex network of passageways and chambers. During floods or heavy rainstorms, these passageways will full up with water and force the ants to evacuate their home. Instead of scattering individually, fire ants (Solenopsis invicta) have the unique ability to gather together as a colony and form rafts on the surface of the rising waters using their own bodies. A layer of ants on the bottom of the raft serves as a base for the rest of the colony to "comfortably" mill around on. Due to the tightly knit "weave" of the ants, water cannot penetrate the raft allowing the ants to stay dry. This water-tight nature provides the raft with the buoyancy force necessary to float. The ants can remain in the raft formation for weeks if necessary or until the floodwaters subside and they are able to establish their colony in a new underground home.
(video link courtesy Nathan Mlot)
There's a lesson to be learned here: By sticking together, all the ants survive. If the ants on the bottom don't stick together, the ants on the top will drown. If the ants on the top don't help the ants on the bottom stick together, they will all drown.
“Go to the ant, you sluggard; consider its ways and be wise!" -- Proverbs 6:6