Minecraft Win10 Edition, helps the enchantment (on the turtle shell) bulletproof 4 what against Guardians / Guardians underwater?

I'm unsure. LG

No does not help. I would rather recommend you general protection. That works

Okay thanks!

What enchantments do you recommend to me on the turtle shell?

https://minecraft-de.gamepedia.com/...6tenpanzer

Here are all enchantments.

Protection Durability, water affinity, breathing, thorns or repair are always the most sensible.

I think you want to conquer an oceanic monument. So you should take thorns, protection and durability / repair if possible water affinity brings nothing because you will get any degradation anyway. However, I would advise you to bring some potions for underwater breathing and night vision, The helmet is useful only a few seconds something.