They sort of had me in the beginning, but it gradually got worse as the story progressed. It got boring, and the plot is kinda shit.

This might be a matter of genre and target audience, but I think that the time they spent running at the beach and playing with water, should have been spent developing the characters and their stories on a deeper level.

It would have also been better if they leaned more towards the psychological part of the story, but they rushed it, and even completely brushed it off in some cases, where they could have dug deeper into it.
Jo Taehyun is such an interesting character, with a traumatising past that still haunts him in the present, and yet it feels like his story was cut short. An example is the flower pot scene. They could have made a bigger deal out of the incident, or even dramatized it.
The plot had potential, but a lot of things were simply executed badly in this series.

And would it kill them to show a little skinship? Okay, they spend the final episode going on a trip together, after yet another time skip. And if I’m not mistaken, they are now a couple. So why are they avoiding physical contact, and acting like they despise the thought of touching each other? Is this a matter unfortunate chemistry, or bad directing?

Cinematography was basic and nothing special, and so was the OST. Would not watch it again.
It felt like the creators left a huge stuffed luggage unpacked, and that really bothered me.