I just saw "the movie that shall not be named" about PH ..

[Halsey]

ORIGINAL: Sarge

ORIGINAL: Halsey

Kate Beckinsale!!![&o]

It's the ONLY reason to watch that stupid movie.
Oh, and maybe James King too.[;)]

[Viper6]

ORIGINAL: carnifex
A .50 caliber FMJ round, fired vertically, will penetrate a 1 inch pine board up to 5 feet under water. Fired on an oblique angle, the penetration is reduced by 1 foot.

A .30 caliber FMJ round, fired vertically, will not penetrate a 1 inch pine board at 2 feet under water.

Military FMJ rounds do not "explode" or expand. Under water they will simply expend their energy and sink. Whatever Mythbusters was firing was not what you would have been strafed with, that's for sure.

"Fragment" is generally the word used, and military FMJ rounds will indeed fragment on impact - in fact the current NATO standard 5.56mm round gets almost all of its killing power when it fragments on impact with flesh. Fragmentation depends on ammo type and velocity, generally a bullet will fragment on contact with human flesh anywhere above ~2800fps, water should be slightly harder durring a high-velocity impact, but the number should be about the same. Mythbusters didn't do a very good job of testing this as most of the weapons they used were either handguns (800-1100fps) or high-power rifles (2800-3200fps). The 2800fps number is based on FMJ ammo, while a AP, APSC, or SLAP round would improve water penetration it will also decrease the likelihood of a lethal wound should the round actually hit anyone. Mythbusters though was probably using standard civilian softpoint ammo, which would have made  fragmentation more likely.

Now, I don't know as much about WWII aircraft weapons as modern systems, but don't most aircraft use explosive ammo to increase damage to other aircraft or ground targets? If that was indeed the case in WWII those rounds should not have penetrated water at all but simply exploded on impact.

[SGT Rice]

Actually PH follows in a long and distinguished Hollywood tradition of ignoring history and common sense, just making it up as the script goes along.  Remember these classics?
 
The totally bland MIDWAY [>:] - Not an F4F in sight.
 
The oscar-winning PATTON  - German M48s (Pattons!) vs US M41s in North Africa.
 
The ridiculous U-571  - valiant American sailors steal a U-boat in the middle of the Atlantic, then have to fight off German subs, destroyers and single-engined fighters.
 
And the truly awful BATTLE OF THE BULGE  - same tank lineup as PATTON, with the valiant American defenders immolating Panzermeister Robert Shaw by rolling barrels of gasoline at him.
 
 
But let us acknowledge the valiant few, those noble producers and directors who actually try to get it right (usually by hiring Dale Dye).
 
SAVING PRIVATE RYAN - sure, the storyline didn't make sense (as the GIs kept repeating throughout the movie) but every piece of gear in that movie looked right; who else has tried to realistically recreate German halftracks, towed AA guns, Kettenrads, Marders and Tigers in one movie?  I really appreciated the effort.
 
PLATOON - Vietnam's a little easier to get right, all the original hardware is still lying around; but this was still a beautifully made film.
 
BATTLEFRONT - A classic; haunting B&W character study of a platoon of Screaming Eagles at Bastogne.
 
and my personal favorite ... [&o]  KELLY'S HEROES - quite possibly the greatest war movie ever made [;)] 
(just discovered that the Tigers (actually T34s with implants) used in this film were used again in PVT RYAN).
 
 

[Cap Mandrake]

The ridiculous U-571 - valiant American sailors steal a U-boat in the middle of the Atlantic, then have to fight off German subs, destroyers and single-engined fighters.

[;)]

[Nomad]

forget it, new board software doesn't seem to be working right

[Viper6]

lol, didn't mind U-571 actually, not accurate at all really but still an entertaining movie - kinda; only enough to make me see it once though.

And for the movies that got it right, Blackhawk Down is definitely among the top 5 or so.