Shape Water Question

[Galgano]

If I shape the water into the form of a sword, like say a short sword, would that count as a short sword, an improvised weapon, or something that the DM would decide on a case by case basis?

[Avigor]

First, you'd have to freeze it, and you'd be wielding a chunk of ice shaped like a sword so it would probably be an improvised weapon and follow those rules (which I do believe allow you to use approximately equivalent weapons to determine the item's damage).

[Galgano]

So regardless of the damage, I would have to be proficient in improvised weapons to be able to use it effectively?

[Quoxis]

So regardless of the damage, I would have to be proficient in improvised weapons to be able to use it effectively?

If you're doing it just because it looks cool, talk to your gm. Maybe they'll allow it to be a normal weapon; it'd take two actions to make, so you'd be at a disadvantage in combat anyways.
Other ways: pact weapon of a warlock or the eldritch knight's bonded weapons - just fluff your magically appearing sword to be made out of ice.

If this is just meant to be a question regarding icicle weapons: if you're proficient in the kind of sword you're making, you can potentially treat it as such a weapon, completely with proficiency and everything according to the section about improvised weapons (iirc)* - if your gm allows it (see above).

*the way i remember improvised weapons: if it's close to a weapon, treat it as such, if it's weird - a wheel, a stone, a dead kobold - get the tavern brawler feat.

[Ventruenox]

PHB Errata indicates that all PCs are proficient with Improvised Weapons. Tavern Brawler is not needed to deal 1d4 with an Improvised Weapon.

Ice is also quite brittle. You may only get one attack with it before it breaks into an unusable form.

[JackPhoenix]

PHB Errata indicates that all PCs are proficient with Improvised Weapons. Tavern Brawler is not needed to deal 1d4 with an Improvised Weapon.

Errata mentions only that everyone is proficient with unarmed strike. Nothing about improvised weapons. Tavern Brawler never was needed to do 1d4 damage with improvised weapons, but it is still needed to add your proficiency bonus to attack with them.

[MaxWilson]

So regardless of the damage, I would have to be proficient in improvised weapons to be able to use it effectively?

Not necessarily. The PHB says that if the improvised weapon resembles a weapon type closely enough, the DM can rule that it is effectively that kind of weapon (so proficiency applies as normal). If it doesn't resemble anything, then it does only 1d4 and you don't get proficiency bonus, unless you have Tavern Brawler or something.

I can definitely see making a club out of ice. A shortsword? ...Maybe if the tone of the game is already pretty casual, then sure. But in a more serious game, hmmm, well, ice seems unlikely to be sharp enough for a cutting edge... then again, shortswords are for stabbing, not cutting... so I can imagine letting it be an improvised shortsword that degrades over time (-1 to damage, cumulative, for every hit after the first might be a good place to start, just to get things rolling--after the fight, I'd discuss with players whether that seems reasonable, whether the rate of decay feels right and whether it's right that misses (which could also be parries) don't degrade anything).