No. In fact, historically, compound bows were frequently
made with water soluble glues, meaning if you tossed it in water, the bow would
come apart in thin strips. Some modern bows can (probably) survive the
experience, but it’s still something you’re cautioned against doing. Off hand,
I’m not sure what water would do to a sinew bowstring, but I’m fairly confidant
the results wouldn’t be pretty.
I’m not sure, exactly, how a waterlogged modern bow handles.
The advice is, usually, to dry the bow, or allow it to dry off naturally rather
than continuing to use it. Then, with mechanical bows, re-oil it if necessary.
With most melee weapons, you don’t really want to get them
wet, but it won’t do much damage to them. Depending on the grip, it may make
them harder to hold. There are some edge cases, if you have a melee weapon that
can absorb water, and become waterlogged, then that will affect its use. I’m
thinking of an untreated wooden club, but there’s probably some other
possibilities that haven’t come to mind.
Firearms are a little more complicated. Black powder does
not burn when wet. Hence the idiom, “keep your powder dry.” A musket with wet
powder is worthless. This is compounded by the fact that early firearms needed
to have some means to access the powder (up into the 19th century), so dropping
one in water would ruin the load, and make the gun inoperable.
Once dried out, black powder is good to go again. Usually
you’d do this by spreading it out over a clean surface and allowing it to sun
dry. Normally this should only take a couple hours. Waiting for a loaded charge
to dry out could take a while. (I’m guessing a couple days, but it honestly
could be longer.)
Modern firearms (using a sealed cartridge) will fire
underwater. The ballistics are wonky. As, I recall, the bullet will lose almost
all velocity within five or six feet (this applies to both pistols and rifles).
In most cases, a modern firearm that’s just been submerged will be good to go
as soon as it gets above the surface. There are probably a few rifles that don’t
take well to water getting into their gas return system, but none come to mind.
In general, you don’t want to get your weapons wet, but if
it happens, this isn’t the end of the world. Bows are an exception, though.