Many No Man's Sky players, myself included, have wished that when piloting our ships over a planet's surface, we could fly closer to the ground. Well, our space-prayers have been answered. The LowFlight mod, by Hytek, allows you greater control over your ship's altitude, meaning now you can really skim the surface, fly between trees, through valleys, and under those hovering rocks alien planets always seem to have for some reason. You can even fly directly inside caves, as you can see in my gif above.
The reason this mod is so helpful is because it can be hard spotting items of interest on the ground from the altitude we're typically forced to fly at, particularly if said items are slow to render. This also makes landing where you like a lot easier: who hasn't released a gusty sigh when realizing that monolith you tried to land next to is actually a four-minute walk away? Now you can get nice and close before setting down.
If spaceship spelunking isn't enough, you can also fly underwater. I've tested that too, though it's not a heck of a lot of fun. Your viewscreens go blank, and you can't really make out all the lovely underwater features. Still, it's step above our ships refusing to fly below 1,000 feet except when landing. Below, you can see a video of the vanilla flying height and the modded one. It really does make a big difference.
Be warned: flying low means you might smash into rocks, trees, and mountainsides, all of which will damage your ship, and quite severely. I can attest to this: I destroyed my ship three times in about five minutes of playing with this mod. Caves, especially they're not very roomy, your ship isn't meant to fly inside them, there are tons of rocks jutting from the ceiling, and it's hard to back out of them. Also, a general warning: this is a mod, and might mess up your game in other unknown ways. Proceed with caution on all fronts.
Installation is easy, and only requires a single file to be dragged and dropped into a folder. You can find the instructions here.