Seanan McGuire‘s Rolling in the Deep is basically a found-footage horror B-movie in novella format. You already know the end result from the very start so what stands out is the lead-up; the anticipation of ‘how’. And, unfortunately, like quite a number of stories in this genre the ultimate reveal is the part that’s lacking. Other issues would be the token deaf guy, the sudden comic-relief-like shift to the aggressors’ perspective, and the way the mermaid performers die so nonsensically.
The follow-up to the above is Into the Drowning Deep, a full-sized novel which does not require having read Rolling. This is much, much better in practically all respects with the only real issues being the strange behavior of the captive and the inclusion, once again, of what appears to be token deaf characters (though to be fair, their presence here at least has some plausibility to it). The ending is also pretty open.