I think you're kind of nitpicking at it here
1: Would a scene where he picks up his phone or goes outside to scream help really do much at all for that scene. I get that it kind of doesn't make sense where one-second shes drowning and the next second she's suddenly in the ambulance with not even an oxygen tank or but who knows. Like i think back about that scene now since she was chained down, how did she get out of that. Scenes like this just take up screen time as the drama is winding down because it just takes up time whereas there's still a lot left for the drama to explain/ finish up. The police chase i feel like are one of those where the driver speeds up and magically loses track of the police, these scenes are kind of common in dramas because they need that antagonist to still be there for the drama to conclude rather than have him taken in to police , problem solved(that would be too easy). It's frustrating but i've seen alot of dramas do this anyways, this is not the only one. and besides phones these days are waterproof or at least water resistant to a point this won't stop a person from using the phone entirely.