Shooting a bullet into water

No, its not true.
A bullet striking any object will slow down, even if it changes direction.
It may not slow down much, but it will slow down.

no.

It is possible--it would depend upon the angle of incidence, and the weight of the projectile. It is, however, unlikely. It is not unknown, certainly, although the cases of which i know involve solid shot fired from cannon, with a low muzzle velocity and a high angle of incidence.

In the fight between HMS Java and USS Constitution, the American gunners, early in the fight, "skipped" solid shot off the surface of the water causing the cannon balls to strike Java just above the waterline, with devastating effect. The most lethal projectiles in such battles were not the cannon balls themselves, but the heavy splinters of oak which were flung at very high speeds from the planking of the hull when struck by a cannon ball. The shots which Constitution "skipped" into the hull of Java sent splinters flying all over the gun deck, inflicting serious wounds.

So, it is certainly possible for such a thing to happen. I believe, though, with modern high-velocity firearms that it is unlikely.

A clarification--both MM and Dys are correct, the speed of the projectile will not increase. But it is possible for projectiles to ricochet on water.

Whether the speed increases or not, it is unsafe to shoot at water according to this source:

http://www.newboldtargets.com/top-header-pages/newbold-targets-shoot-safe.htm

" Never shoot a bullet at a flat, hard surface or at water. Make sure backstops and berms are adequate during target practice. For example, fire bullets into sand, soft dirt backstops and properly constructed steel bullet catchers."

Thats not true either.
While I always thought it was, the show "Mythbusters" on the discovery channel did a show on exactly that one time.
They proved that the splinters are not as deadly as the cannonball, and they also showed that the splinters didnt penetrate flesh to any degree (in this case they used pig carcasses as a standin for humans.

http://dsc.discovery.com/videos/mythbusters-cannonball.html

Mythbusters is hardly a unimpeachable source. As i understand it, the Mythbusters program used 6 pounder shot. Java was equipped with 18 pounder long guns, and 32 pounder carronades. Constitution was equipped with 24 pounder long guns, and 32 and 48 pounder carronades. There is a huge distinction to be made between the effect of a 24 lb. solid shot and a 6 lb. solid shot, never mind the effect of 32 or 48 pound solid shot from carronades at close rang (carronades could only be used at close range). There's a hell of a difference between the effect of a tennis ball size projectile and one the size of a bowling ball.

I did say "lethal," which was ill advised. But the accounts of battles at sea, which all Royal Navy and United States Navy officers were required to submit, show that splinters accounted for the majority of casualties in their engagements. I acknowledge that they weren't necessarily more lethal than solid shot (leaving aside post-trauma sepsis). If one wishes to discuss lethality--grape shot, bar shot and chain were very likely the most lethal.

And, by the way, all ships mounted splinter netting immediately behind the hull on the gun deck, and over head. All ships also used bar shot with the specific intend to inflicting splinter damage. Those boys at Mythbusters usually show a profound ignorance of their subject. If i recall correctly, they were talking about pirates. It may well be true that pirates used 6 pounder guns (although such guns were uncommon--four pounder or eight pounder were more likely). But Java was rated for 38 long 18s, and Constitution was rated for 44 long 24s. Neither ship, however, necessarily went into battle with their rated armament. Constitution, for example, usually mounted 30 long 24s and 20 32- or 48 pounder carronades, with two 24 pounder bow chasers. Both ships used swivels mounted on the taffrail and in the fighting tops.

There's a world of difference between the effect of a six pound shot and the 32 pound shot of a carronade.

Mythbusters were talking about pirates (who didn't want to necessarily damage the ship they were attacking) and they tested six pounders. Naval vessels were a very different kettle of fish. As i've said, there's a world of difference between the effect of a six pound solid shot and a 32 pound solid shot.

Click here for a discussion of the Mythbusters topic at "Ask-Metafilter-dot-com."

I was simply responding to your use of the word "lethal", nothing more.

Note the remarks about the splinters from 18 lb. and 24 lb. shot (to say nothing of 32 lb. shot) being the size of sections of 2 x 4, rather than the pencil sized splinters in the Mythbusters test. Note also the point about naval vessels being constructed of oak.

I understand that, but that still didnt acount for the majority of casualties.
Many of the British sailors killed were killed by US Marines firing from the tops, and most of those killed below decks were killed by shot, chain, and explosive shot.
The splinters themselves, while dangerous, didnt kill as many as the other weapons did.

That is all I am correcting, not the rest of your argument.

"The armament of a ship-of-the-line consisted of two or more horizontal ecks of iron cannons that fired solid iron balls weighing from eighteen to thiry-two pounds a distance of several miels, though the ideal rang was much shorter. Indeed, most ship captains of the age believed that the optimum range for a ship was a "half pistol shot"--about one hundred yards--from which distance an enemy vessel was hard to miss. A ship-of-the-line might carry between 60 and 120 such guns, but by the outbreak of the American Revolution, convention had established 74 as the proper number of guns for a battleship. A single broadside from a seventy-four-gun ship-of-the-line sent more than eight hundred pounds of iron hurtling toward an enemy vessel to smash into its wooden hull and create giant splinters of wood that flew across decks crowed with men." (emphasis added by me, of course)

From a Google cache of the Naval Institute Historical Atlas of the U.S. Navy

You seem to think I'm disagreeing with what you are writing.
I'm not for the most part.
I have acknowledged that wooden splinters were dangerous and could be lethal.
I also acknowledge the fact that there is a big difference between what ships of the line were armed with as compared to a 6 pounder.

I am simply saying that splinters were not the most lethal part of a naval battle for wooden ships.
Snipers, chains, explosive shot, and Fire shot were all more lethal to sailors then.

Your "correction" is, so far, unfounded. When HMS Phoebe trapped USS Essex on a lee shore at Valparaiso in early 1814, and defeated her with long range gunnery (Essex mounted only carronades, and could not reply at that range, and could not claw off the lee shore to close the engagement), the American casualties were relatively high for the times. Phoebe stood out of carronade range, and therefore could not use grape, nor could her marines and sailors in the fighting tops use their muskets, being out of range. According to James' Naval Occurrences, Essex had 24 men killed and 45 wounded. Captain Porter, commanding Essex, however, reported 58 killed or mortally wounded, 39 severely wounded and 27 slightly wounded. None of those were killed or wounded by Marines in the fighting tops when the engagement took place outside the range of carronades.

The American sources for this action are, of course, Captain Porter's report--but also the memoirs of Admiral David Farragut, of Civil War fame, who shipped in Essex as ship's boy in 1813, and was rated midshipman by the time of the engagement with Phoebe.

Now, you can claim that all of the casualties were inflicted by direct hits with round shot, but don't expect me to believe that.

I've already acknowledged that i ought not to have used the term lethal. You have failed to convince me, however, that splinters did not cause the majority of casualties. And, apart from a mention of the Mythbusters program, which tested nothing about the effect of 18 lb., 24 lb. or 32 lb. shot, you have mentioned no sources.

I'm not sure how that contradicts MysteryMan's thesis.

He states a belief that smaller arms were more lethal than splinters from larger armaments. You then counter with an example in which none of the smaller arms were used....

Nobody is saying that the larger armaments were not effective. They certainly had greater range, which is the lesson I take from your example.

Then why are you still arguing?

Do you have reading comprehension problems?