I am reminded of an old illustration. Oddyseus is clinging to a wooden raft while Posiedon tosses him about the sea. Now Old Oddyseus was something of a sailor but still looked rather uncomfortable. A flooded area is one of the most dangerous waters to travel. You have uncharted hazards to navigation both submerged and afloat, new and changing currents, spilled toxins and fuels waiting to ignite. And into this somebody wants to launch a bathtub, designed to HOLD water and not displace it in a manner pleasing to a naval architect sailing his Concordia. being in a flood is no different than being lost. You need to secure a safe place and wait for rescue. If you must water-bug out, do so with a proper small boat.