I am a massive fan of Pelicases, or the similar design cases, they are properly water proof and you can open them and see inside. So much better than the big jar type.
For years we have supplied them to sailing clubs and if anyone can break something it is either a safety boat driver or a squadie, Pelicases are tough enough for either.
Once you have your cases, perhaps one for flares and one for first aid or similar, they are easy to stow without mounting.