The US Navy investigated how reduced body temperature affected our mental capacity. Not surprisingly they found that every degree in reduced body temperature reduces your mental capacity by 10%. Worth considering, isn´t it? Almost all diving is done in waters colder than your body temperature. The longer the dive, the more you freeze. You simply should insulate against the cold water and get some protection against anything that may cut, stick or hit you. But a wetsuit or drysuit, trilaminate or neoprene? Lots of different options and difficult choices. New materials are introduced and innovative designs released.
One safe way is to follow the path of the pros. Join the Poseidon drysuit users. You´ll be in great company, rom commercial to military and technical divers all over the world.