XRay mod will give your character x-ray vision, which will greatly facilitate survival. It can be called cheating because with it you will be able to quickly find even the…
XRay mod for Minecraft 1.8.9
Minecraft 1.8.9 (December 2015) is the last 1.8 patch and the one Hypixel-era Forge mods target. An XRay mod differs from the texture pack in one thing: it has a switch. The world looks normal until you press X; then stone, dirt and the other filler blocks go invisible, ore and chests stay, and a second press brings everything back. The list of highlighted blocks is editable, so you can leave only diamonds and ancient debris, or add spawners and chests.
On 1.8.9 the mod is Forge-only: XRay Mod for Forge or the older Julialy’s X-Ray, which also has a cave finder and a fly mode. Install Forge for 1.8.9, drop the jar into the mods folder, start the game.
Ore on 1.8.9 sits in the classic layers: diamonds under Y 16, redstone and lapis in the twenties, gold under Y 32. Stand at Y 12, press X, and the diamonds within render distance are the blue dots along the bottom.

Servers
Keep it off on public servers. Anti-xray plugins on 1.8.9 send fake ore to the client, so the mod shows garbage, and the mining pattern itself gets you flagged. Singleplayer, LAN and your own private server are the places for it.
Prefer no mod loader at all? XRay texture packs for 1.8.9 do the same job through resource packs.