i cant seem to find trhe new underwater crtates in the data files i even reset it so was default can anyone help me with this please

I had the same issue 
https://umod.org/community/better-loot/23016-crate-toolsprefab-2?page=1#post-11

You have to get the name of the prefab for that loot box

If the list is current you should find what you need here
https://github.com/OrangeWulf/Rust-Docs/blob/master/Extended/Prefabs.md

Add this to your oxide/config/betterloot

"assets/bundled/prefabs/radtown/underwater_labs/crate_ammunition.prefab",
"assets/bundled/prefabs/radtown/underwater_labs/crate_elite.prefab",
"assets/bundled/prefabs/radtown/underwater_labs/crate_food_1.prefab",
"assets/bundled/prefabs/radtown/underwater_labs/crate_food_2.prefab",
"assets/bundled/prefabs/radtown/underwater_labs/crate_fuel.prefab",
"assets/bundled/prefabs/radtown/underwater_labs/crate_medical.prefab",
"assets/bundled/prefabs/radtown/underwater_labs/crate_normal.prefab",
"assets/bundled/prefabs/radtown/underwater_labs/crate_normal_2.prefab",
"assets/bundled/prefabs/radtown/underwater_labs/crate_tools.prefab",
"assets/bundled/prefabs/radtown/underwater_labs/tech_parts_1.prefab",
"assets/bundled/prefabs/radtown/underwater_labs/tech_parts_2.prefab",
"assets/bundled/prefabs/radtown/underwater_labs/vehicle_parts.prefab"

Then they will be generated in Data file to edit.