Much like many of the side quests in Horizon Forbidden West, the Tallnecks in the game require a lot of thought to override. It's not a simple jump and climb job. One of the later ones, the Landfall Tallneck in Horizon Forbidden West, is tricky, so we've got a walkthrough on how to override it.
Tallnecks Explained
You probably know how Tallnecks work in Horizon Forbidden West by this point in the game, but overriding them is important in your quest to reveal all of the opportunities on the map.
The Landfall Tallneck is one of the final Tallnecks you'll encounter, revealing much of the map to the far west.
Landfall Tallneck in Horizon Forbidden West Guide
Once you've reached the location, on the coast of the western most point on the Horizon Forbidden West map, you'll notice the Landfall Tallneck in the water, it's head poking out of the waves.
Swim over to it and you'll need to examine two missing parts on its back. Now to head out into the surrounding area to find them.
First Landfall Tallneck Part
Swim into the area marked on the map and look for a small ruin with a crate on it. It's one of those crates with blue markings that indicate you can use a Pullcaster on it.
While there, shoot the red section of the ladder on the other side (there maybe a Frost Glinthawk on top of that other ruin, so kill it first).
Press traingle to grab the crate and push it into the water. Then jump into the water and go into the gap in the wall of the ruin with the ladder on.
From there, pull the crate nearer to the ladder using Aloy's Pullcaster.
Then, jump onto the crate and climb the ladder, being sure to loot the machine on your way.
Now, run across the rope that crosses to the larger ruin and turn right once you get there. Then, jump over the gap to the next section.
Finally, grapple onto the next section and kill the two Frost Glinthawks that'll attack. Now you should be able to grab the part from in front of you or up the short stairs.
Second Tallneck Part
Thankfully, the second Ladfall Tallneck part in Horizon Forbidden West is easier to grab.
Head to the ruin further north east, which you'll see in the screenshot below, and then head around the back of it, along the low ledge.
Then, jump up the rubble and onto the roof of the ruin and head up the stairs on the other side of the wall. The scrap pile in front of you should contain the Tallneck part you're after.
You can then head back to the Landfall Tallneck, install the two missing pieces you've collected, and then find a place to jump onto it.
If you head to the part of the ruin that's furthest out to sea, you should be able to jump onto it from there.