Achivements? Why bother with them? They are all lame and useless. Just as crossbows, lol.

I'm not, I'm just playing the game. I just happened to notice the achievement exists in the list of achievements, I'm not trying to achieve it.

Crossbow very usefull underwater. Or while sailing through Skellige waters. It's also quite usefull to bring down nauty flying creatures.

Sorry, OP, but this is your lack of skill only.

I'm not saying the crossbow is a great weapon in Witcher 3 - it's a clumsy tool for limited uses.
But it does work. And if you bother to aim, you can hit quite well specific parts ("nutshot!"). I killed enemies 5 levels above mine with a crossbow and a bit of time, just for the hell of it.

So, if it doesn't fit for you, don't use it. Works for others. That's indeed a very strange thing. Feels like they didn't get the original idea for underwater fights working (or didn't have any?), so tacked on automatic crowsbow quad-damage when underwater. Very strange, that. I agree on that. I don't care much for the achievements, so I probably won't do it just for you... but it's not hard. really. Just takes persistence and time. (Unlimited ammo comes included with the crossbow)

I have no time (read use) for achievements, but I agree with the above. Think about it: drowners/sirens etc. swim at you (mostly) head first under water, and there's absolutely no shortage of them. Two plus two.

Oh I've got no lack of skill with the crossbow. My username "skeletonbow" comes from back in the days when Half-life came out and I cozied up to the crossbow as my main weapon, easily taking out 5+ enemies in less than 10 seconds fairly often. Came in 2nd place in a tournament. My skill with aiming weapons in FPP/TPP games is not lacking.

I'm not shooting bolts and hitting trees, they're hitting their mark exactly where I want them to. Hit someone in the head with the best bolts and it does the damage a tennis ball might, that's my experience. Have I killed anyone with the crossbow? Absolutely! After standing just out of the jail cell range the game puts them in where I can hit them but they wont bother coming to me, then firing an endless number of bolts with probably a 95% hit ratio, several headshots. You say yourself "and a bit of time", and that's exactly what I mean - you can't kill someone on land with a single shot that I've seen although if someone has a video of them doing headshot kills on land with the crossbow I'd love to see it. Maybe if you're like level 35 and shooting level 8 monsters/people perhaps you can get a single shot headkill, but I've yet to see anyone go down on land with a single bolt including exploding bolts which is pretty silly. I just nailed a guy in the face with an exploding bolt - a pirate, and his immersion-breaking reaction was a temporary delay of a half second followed by charging me with his sword. A bare-chested pirate, so no armor protection at that. An exploding bolt. I'm level 27 or 28 and he was about level 18. Head shot! That's just so unrealistic.

Unless you mean you have to hit them in a specific eye socket or something in which case yeah, I can hit them in the head but I can't hit them in a specific eye socket so if that is necessary then I suck. :) Yeah, again I'm not saying people can't be killed with the crossbow - I've killed enemies with it, but only after slugging them with over 10 shots with multiple headshots. My claim is that the achievement of killing 50 enemies with single-shot headshots just seems ridiculous with the current implementation of the crossbow unless it is counting underwater headshots in which case Geralt could accomplish that shooting with his feet with one leg tied behind his back. He practically kills enemies just by taking the crossbow off his back underwater without even putting a bolt in it. :)

For such an amazing game though, the crossbow is one hell of an immersion breaker requiring serious suspension of disbelief. Perhaps it was added as you suggest for underwater due to lack of a better underwater combat mode. The underwater combat does seem pretty weak and arcade-style like House of the Dead or something rather than RPG style.

There is one thing I have not got to try yet that I've been itching to try though with the crossbow, and that is to shoot an exploding barrel with an exploding arrow to see if it will ignite it. That would be a nice way to take out bandits and drowners near exploding barrels.

The exploding bolts are also pretty cool. Witcher version of a rocket launcher.

Oh, on that I agree wholeheartedly! Sounds a bit like Duke Nukem or similar FPS ;)

I just looked at that achievement and the description says nothing about one-shotting. Just killing non-monster opponents by shooting them in the head with the crossbow.

I finally got an opportunity to shoot an exploding barrel with an exploding arrow! Basically... absolutely nothing happens. Not well thought out that.