Twin Huey Man - speaking as one of the most current HUET qualified pilots in NATO (I did my requal this morning) your chances of 'swimming around' and helping someone else are somewhere between none and F-all. You can see almost nothing in a benign environment like a swimming pool without goggles or a mask and you would see even less in the sea, and that's in good light. The bottle is there as a secondary escape system should you fail to get out quickly - not to make you Marine-Boy/Navy Diver/Hero of the day.
The bottle should give confidence to dispel fear, not breed over-confidence.