It can, but there are actually very few of those types of subs around and they tend to be limited to research and recreation. Keeping several hundred tons neur

It can, but there are actually very few of those types of subs around and they tend to be limited to research and recreation. Keeping several hundred tons neurally buoyant is kinda hard and if the sub has positive buoyancy then it requires propulsion to stay down or else an elevator ride to the surface is a one-way trip. Needing constant propulsion is bad for a military sub, and being stranded on the surface after any sort of emergency surface action (even a test) would also be a bad thing.