I swear I've seen this on YouTube via a post on Reddit within the last couple of years. I think it was an r/tipofmytongue solve but I've been unable to find the post again.
It's a live action commercial or bumper with a bunch of people in a public pool. Santa's corpse is floating face-down and people are surprisingly nonchalant about it. There's some interaction with a person on the side (a lifeguard maybe?) who might have prodded at the body with something.
I'm pretty sure it had to do with a TV service; DirecTV and Spike come to mind but it might not have been either of these.
Did quite a bit of searching. Couldn't find any reddit posts other than yours, or commercials/bumps that were similar.
It's quite an unusual setup for a commercial or bump (and a bit morbid for a DirecTV commercial). Do you remember what the gag was? Are you sure Santa was dead, and didn't come to, near the end of the commercial? Do you remember how the concept was being used to sell or advertise something?
Could this have been part of a larger, darkly comedic sketch? Do you remember seeing the Adult Swim logo?
The original post was someone announcing they'd found it themselves after a lengthy personal search. They also mentioned having posted about it on the Lost Media sub which might be why I was so convinced I'd seen it on Reddit.
No idea why I didn't search the server for this before though lmao