The large lasers are ER versions; they outrange everything but LRMs, Gauss Rifles, and ER PPCs.<br/><br/>And yes, all 'mechs are NBC sealed; they can walk across the seabed for hours at a time until the internal oxygen scrubbers in the cockpit need to be refreshed. If there's a breach, that section of the body is rendered useless, however, so try not to get shot in the centre torso; no engine = dead 'mech = slow lingering death by carbon dioxide poisoning if the pilot's underwater.<br/><br/>(Note: I wrote this at 9 AM, before I had to go to work, just before my router crapped out; It's now 2 PM, so... :P)