ETOPS =Extended Twin Operations Performance Standards. Requires Twin engine, and separate crews to work on each engine/part. This is to ensure that if ANY minor error/flaw/oversight is done by one crew on 1 engine, it won't be done on the 2nd engine. It basicly guarantees that a plane can be furthur than 1 hour (original ETOPS) from a diversion point, but as engines have evolved, it has gone to 120 min, and 180 min. There are even proposals for a 240 min extension. This time period is the time that the plane should be able to cruise, without undue stress or performance decline on 1 engine.

Many planes have the capability to be ETOPS certified, but maintaining the rigid maintenence requirements and certification process is very costly/inefficient. Most 777, 767, 757 and even 737 of Boeing can be certified ETOPS rated as well as A300,310,320, and 330. That doesn't mean that the airlines flying them have a use for the additional cost of maintining a A320, when it may never fly over water or away from diversion airports (Theodore)

As for the "overwater models" they will have life rafts in addition to the life jackets standard, and the safety card on your particular aircraft will point out this feature (along with nifty little illustrations of the boats in use!)