Targeting a Swarm with Polymorph

Can you target a swarm with Polymorph to turn it into a single creature?

RAW? Yes, there’s nothing preventing you from doing it, the stack of immunities that one gets doesn’t prevent Polymorph from being used on it. RAI, I’m not sure, I think they talked about this once.

Quote from wagnarokkr >>

[...] various rulings that Druids can't use Wild Shape to turn into a swarm because it's not an individual Beast. [...]

 Yeah, for example, this is from the Dev:

@TStrek22 can druids wild shape into swarms?
@JeremyECrawford Wild Shape lets you transform into a single beast. A swarm is a collection of beasts, not one.

EDIT: adding the quote.

A swarm is treated as a creature with a list of resistances and immunities. Given that swarms have immunity to being petrified, it's probably intended for them to be immune to polymorph effects, but as written they aren't.

I'm not a big fan of the swarm rules, I prefer something like "Swarm Defense: a swarm is resistant to damage and immune to conditions from effects that do not target an area".