In this analytical work, the transient behavior of a flooding cargo vessel is studied. Damaged underwater compartments, especially those at the keel depth, are very critical in terms of sudden stability change. While it is essential to know beforehand the amount of water flooding the compartment, thus the damaged stability, it may also be crucial to estimate the time for final damaged stability, as well as the air pressure accumulation and the temperature build-up in the watertight bulkhead. Calculations are performed using Ship Stability, Thermodynamics and Heat Transfer principles where air is assumed to be compressed isentropically due to incoming water. Proceeding the flood, the compressed thus heated up air dissipates its excess energy to the environment resulting in air volume decreasing an further flooding. At the end of these processes, the final steady state is attained, following the end of the transient behaviors of physical conditions.