It's really more like 3 seconds to open it or to fold it back up. Because water has such a dampening effect, no there's not much sound involved, compared to say a diver exhaling through a regulator.
I agree, taking it out, putting it back, swimming, taking it out again, etc... would not make much sense. But say for example you're doing a shore dive, and you're carrying out your fins, gear, game bag or stringer, or whatever else you've got. Wouldn't it be nice while swells are smacking you in the face to not have to worry about dropping your spear while you're putting your fins on, or when your exiting the water. How about climbing back on a boat? Some spearfishermen like it as a handy backup to a speargun. What if you're main purpose in the water some day was other than spearfishing, such as looking at a wreck, practicing your breath hold, helping someone else out; and a great target of opportunity swims by. With the Foldspear, you've always got an effective polespear with you; whether your sole purpose is spearfishing or not. You may want to keep it out and in your hand the whole time, but you dont HAVE too.