No Man's Sky created dreams of swooping through canyons and under rock formations on strange alien worlds, but in practice the game's flight model doesn't let you get closer to the ground than 100 feet. Now a mod has been released to change that: Lowflight by Hytek allows you to crash into the ground and get trapped in caves till your heart's content.
I've had a play around with the mod, wrecking my ship three times in the name of research. It works exactly as it professes to, letting you get closer to the game's terrain and even fly underwater.
However, there are decent reasons for why this limitation existed in the first place, which this mod doesn't address. For one, moving quickly close to the ground is a recipe for getting your ship stuck, especially since collision boxes don't quite match the geometry. For another, moving quickly while close to the ground seems to accentuate the game's already obvious fizzing effect when new detail appears in the world as you draw near.
Whether these trade-offs are worth it is up to you. I do quite like being able to poke around underwater, and I now have hopes of finding an archway or cave large enough that I can fit my ship through. For now, my best efforts will have to do:
The mod can be downloaded at the link above and is easy enough to set up, as there's only a single file that needs to be copied into one of the game's folders. From the readme.txt:
Drag and drop _MOD.Hytek.LowFlight.PAK into your PCBANKS folder (for Steam this is located at Program Files (x86) > Steam > steamapps > common > No Man's Sky > GAMEDATA > PCBANKS)