I would be super careful with any device around sand.
Trust me I am. I'm on the beach 3 times a day, sand gets everywhere both in my car and pockets without any intent. (Heck my car looks like a sand pit by the end of each week)
It's why I like the security of screen protectors and it's how I know about the perils of flip cases
to my own chagrin.
I'm waiting to see the reviews of the S8 official screen protector. Sadly third party ones are normally terrible on every edge device I've owned so far, either they don't fully adhere or the tpu ones like Zagg have a horrid spongy texture and begin curling and lifting if you utilise Gear VR.
TBH the problem looking after an edge device is what made me think of giving the LG G6 a try - and then they went and made it subpar & expensive in Europe.
I never got the opportunity to try the Note 7 official Samsung screen protector despite spending €35 and it sitting in my cupboard
so can not attest to its quality.