could this realy happen

of course, they did it in the movie didnt they? we all know that movies dont lie

Thats all well and true. But the Sonar that was developed to tell you what kind of boat it is was no doubt developed within the past 30 years. The Stingray was an old WWII boat, 50 years old, desiel engine. They made strong points as to the fact that subs don't use desiel. It wasn't so much as incopetant Naval men, or inaccurate sonar, just the fact that the thought was pretty solid that Desiels were out because they were loud, and slow in comparison to others. So when they started hearing singing, and saw the lights... It was pretty obviouse that it was fisherman. Wrongly so, but the fact is that they weren't expecting it, and would expect something different (like running silent) if they did catch it.

"Cute Cat, what's it's name?"
"Annoying Customer..."

Actually,this could happen. Because #1 - passive sonar only tells you how many screws (propellors) the ship (or boat, in the case of a sub) has, and how many blades. It can also tell you the approximate distance (either through direct contact, or convergance zones (donut shaped sound conduits in water), and whether or not it is a surface contact. A diesel sub is the ultimate quiet machine. Unless you catch it 'snorkling' when it runs it's diesel engines to charge it's batterys, or visually on the surface, it could very, very easily do what happened in the movie. Especially the scene mentioned in the original posters message. The advantage of nuclear subs is that they don't have to 'snorkle' (in other words, come close to the surface to recharge), and they don't have to refuel. Otherwise, a diesel sub will ALWAYS be superior in regard to quiet. A nuclear sub still has pumps running to cool the reacter. A diesel sub is using an electric motor. Which is quieter, a pump, or an electric motor?

#2 - active sonor only tells you SIZE and DISTANCE (and bearing, or course, both left/right, and up/down). They STILL use passive sonar to IDENTIFY what type of ship it is, off of it's engine sounds and the propeller sounds. The sound that is sent by active sonor does not reflect off the hull of the ship, as people believe, but actually off the AIR barrier inside the ship. (The metal hull to air barrier in most cases). The person who stated that active sonor can tell you what type of ship it is either knows of something new and top secret that is out there, or is confusing active sonor with SAR, synthetic aperature radar, which can, with SOME precision, tell you the type of ship that a surface ship is by taking multiple radar plots from different angles, comparing it to ships in it's database, and then it takes an educated guess as to the type of ship it is based on size, shape, and it's outline. (the difference between an aircraft carrier, flat with an island, or a battleship, bumpy all over with turrents, for example). HOWEVER, SAR is usually used on surveillance planes because their rapid change of bearing rate can help the computer determine the difference in radar signals. In order for sonar to do this accurately, you might as well be close enough to turn on some high powered lights and look through an underwater camera, because you can't tell much from the hull of a ship except it's size, shape, and MAYBE if it has torpedoe tubes or not (if active sonar really was this accurate). Remember, they were told they were hunting a sub. Every seen the size of a diesal sub to a nuc? It's like comparing a VW Bug to a train locomotive in size. If they weren't TOLD it was a diesel sub they were tracking, then they'd take this bait for sure.

#3) In the excercise, the diesel sub was given an advantage because the nuc captain didn't know WHAT he was chasing. If he was told he was chasing a diesel sub, then most likely, he would have caught the sub. ESPECIALLY if he knew his former XO was in charge, after all they would have know HOW each other thought.

Does anyone care for fruit..... or dessert?

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Yes, this CAN and DOES happen frequently. I was a radar and radio comms specialist for the Navy (12 years I did this job). What Dodge did is a very widely used practice called "Deceptive Lighting". All seagoing vessels (uncluding Navy Ships) are governed by a US Coast Guard Publication called the Navigation Rules of The Road. In this book, vessels are required to display certain colors of lights in certain positions on the ship that aid lookouts tracking them to identify generally what kind of vessel it is and what it might be doing. Using light configurations to make one kind of ship look like another kind at night or in low visibility situations is a helpful way to get warships into a hostile area without the enemy detecting them.(Remember it was early evening, and the weather was getting bad in the movie.) Also, by shutting off certain radars, and other electronic equipment, warships can make the radio energy coming away from the ship look like the transmissions of a civilian ship.....a process we call EMCON (Emissions Control). On the three ships I served on in my Navy career, deceptive lighting and EMCON were drilled and practiced constantly.
--Lord Grant me the wisdom never to judge a man until I have walked a mile in his moccasins.

What I liked best about this movie is that while it was a comedy, the tactics used were real tactics. Though not quite in the way shown for the most part.
Hiding under or on the same bering as a larger, noisier ship for example is a real tactic that can work. However the while "going in between the propellers" ws total bulls**t.
Deceptive lighting IS a real tactic used by the surface fleet. By altering the running lights, navigation lights, and by placing other lights around the ship you can make your ship appear as just about any other kind of ship limited only by your imagination and available supplies. Hanging square sheets over the side and backlit with white light can look like the open hanger bays of a carrier for example.

Diesel Subs are MUCH quieter than Nukes when submerged. a Nuclear Boat has to have the Reactor pumps going all the time. a Diesel sub on batteries makes almost no noise at all

The Orlando was looking for a submarine that they expected to be hiding from them. What they found was a boat on the surface using desiel engines, Lit up with a Mastheaad light and other running lights. and passive sonar picked up a bunch of rowdy singing. Just about anyone would think they found just some boat out for a cruise and NOT the Sub they were looking for.

Sir, Put the mouse down slowly and step away from the keyboard!

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