I’d like to ask the Why is your Ex your Ex participants, and anybody else who’s interested, what you would do in this situation.
This is a story I read in Epic Illustrated many moons ago. It starts off with a female creature of the sea, presumably a siren, singing to the shore. A man in a nearby house hears the singing. He sweats profusely and tosses and turns in bed. His wife is in the other room talking on the phone. You gather that she’s talking to the “other man” and was prepared to tell her husband “It’s over” but couldn’t abandon him when he got sick.
Eventually she hears the window to their bedroom shatter, and she runs in to see her husband has departed through the window and is immersing himself in the ocean, answering the siren’s call. The last panel shows the husband and siren swimming away together.
If you were the one who determined your relationship was over for whatever reason, and before you had “the talk” with your SO, you saw them being taken away by a mysterious entity, how would you have reacted? Would you have been relieved? Angry? Would you have tried to get them back, or at least alerted authorities to the kidnapping?
If they ran off with another human, great. Saves me some trouble. But we still have the problem of getting legally divorced, and his presence might make that more anger-filled.
If they got kidnapped by a human, of course call the cops. The sooner you get them looking, the less likely they are to decide to look at you. More than the minimum that is; SOs are always suspects. And even if I don’t much want to stay married to her, that doesn’t mean I want her raped & tortured to death by some psycho in a dirty white van. Sooner the cops are on the case, the better for her.
As soon as you involve supernatural, all bets are off. Now you’ve got a real problem, at least in the modern world. She will be missed and you may or may not have a good explanation. Of course if when I left for work she was home as usual and when I came home from work she simply wasn’t there, I’d have no idea if she was at the grocery store, under the sea, or away visiting Dave Bowman through the stargate orbiting Saturn.
It’s easy to be convincingly mystified to the cops when you really are mystified. I came home, she wasn’t there, didn’t answer her phone, and wasn’t there at bedtime. Not normal behavior for her at all. So I called you cops. Nope, no note, no nothing. Almost all her stuff is here, but she isn’t. Beats me.
The less you know about the specifics of how she disappeared the better. Specific to the OP’s story, wading into the sea can be an effective form of suicide, and one that often doesn’t lead to a recovered body. Explaining how you were close enough to be sure it was her, but not close enough to intervene is gonna be tough. Unless you do intervene but aren’t quite successful before you need to save yourself from drowning too.
This is an easy question. I’d investigate and try to get her back. Sure, if I was that determined to get a divorce, in the end it might still lead up to that after everything is said and done*. But a chance to investigate something out of the ordinary doesn’t come up very often (obviously not at all in real life). I’d investigate and try to get her back in whatever way seems the most likely to achieve that goal. No Horror Movie Stupid Shit from me.
*. My real life relationship with my wife is quite solid, thank you very much.