Bushwalk Australia

i know theres a thread on thermos only a few posts down, however it focuses on keeping things warm

my question is how effective would a thermos be in keeping frozen meat overnight?

just had a good idea..

thermos 3/4 full of water..meat in freezer bag submersed..freeze whole thing..
being a bigger block of ice will stay frozen longer..and as it melts have drinking water so it saves space/weight
now im in the market for decent thermos.