Do zombies go into water?

[Evangelion]

Usually when we played forest, we built a base next to the sea and just had pillars/walls etc go into water as far as possible so that the enemies can't come from that side.

Does it work the same here? If we build a base on a beach, will zombies come from water or are we safe on that end?

[Shadowrun]

zombies will run underwater in this game now. if you don't kill the wave zombies, they will congregate underneath you in the water and live there forever, downing your FPS, according to a recent post from one player.

[SleepyEyez]

TL;DR: Under certain conditions, zombies will go into water. A base on a sea beach (not estuary) can be safe, depending on how it's designed.

Since I don't know which kind of beach you have in mind, I will explain both cases - sea shore and river shore, but first, some basic info.

Preliminary Knowledge
- Zombies don't float (swim) but travel on foot at the bottom of water. That is, they don't treat water surface as something they can plot a path on. It's the seafloor/riverbed that they plot a path on.

- By default, zombies (and also animals) treat water (a 3D entity) as an obstacle in spite of being able to pass through it.

- If a zombie is somehow inside an obstacle, that obstacle will then not be considered in their pathing calculation. That zombie will plot a path through it, disregarding whether or not the collision causes restriction of its movement. This phenomenon can be easily observed when a zombie is somehow stuck in a tree. In the case of the obstacle that is the water, a zombie that's somehow inside this obstacle called water, will plot a path and move through this 3D water entity towards the zombie's target. That is, zombies don't get stuck inside water like they do inside a tree. This seemingly weird/useless info at first glance is important in the later section of the article.

- When zombies' target is in melee range, they use a different set of more lenient pathing rules for traversing terrains.

- Wave zombies cannot be spawned too close to their target. In my tests, their spawn points have to be at least 500 units (50 Foundations) away from their target. I dunno the max range where a spawn point can be though.

- By default, wave zombies target a random player. If there is no path to that target (i.e. the player is unreachable), the zombies then switch targets to a nearby valid player structure. If nothing is reachable (targets are floating in the air or underground), the zombies will stay as close as possible to their target, usually directly below the floating target or above the unreachable underground target.

- Player structures cannot be build in water but above water.

- Night of the Dead's traps can create looped paths (I call this type of traps loopers); therefore, a base can have openings and be totally safe, instead of being completely walled-off on all sides, because good loopers can stop all zombies including Giants from ever reaching their target.

Wave Spawn Points related to Sea
The theory is that, during a horde event, wave zombies' spawn points are not generated in real time within a certain radius of their target, but instead, are, according to the proximity of the zombies' target, randomly chosen from the pre-defined spots placed by the devs (mostly high in the sky). Note that this is just a theory; ppl are still debating on the topic of how wave zombies are spawned.

Nevertheless, in a rare case, when I was on a boat at the sea, I had seen wave zombies spawning at the bottom of the sea that's close to the shore. That is, the game spawned zombies at the sea between the shore and my character (their target) who was out at the sea.

Still, I have yet to witness wave zombies spawning at the bottom of the sea that's far away from land when I am on a boat at some far away place of the sea.

That is, according to that theory, the devs didn't place wave zombies spawn points far out at the sea; also, the devs only placed a tiny number of spawn points at the sea, which are very close to the sea shore.

Since wave zombies cannot be spawned too close to their target, when their target (player) is close to these rare spawn points at the sea (i.e. those spawn points at the sea are within 500 units of the sea shore base where the player is), there won't be zombies that are spawned from the sea side.

Zombie Pathing
This is about how zombie's target being unreachable affects zombie's pathing.

If the zombies' target is on land inside the player structures that form an enclosure like a box - with player's walls as the 3 sides of the box (forming a U shape) and the 4th side being the shoreline, then the zombies will not plot a path around those walls into that shoreline and then into the box (because water is an obstacle in their eyes). Hence, their target (player) is deemed unreachable, and the zombies will switch targets to a reachable target nearby (player structures), such as those walls that form the U shape enclosure or structures outside the walls.

However, if that unreachable player target inside that enclosure is at one of the 2 corners where the shoreline meets those walls, then the nearby zombies that are within melee range of the player will go around the walls to the shoreline (by entering the water) and then into the enclosure. This is because zombies in melee range use a more lenient set of pathing rules to get to their target as stated in the beginning of this article. So, stay away from those 2 corners where the shoreline and walls meet.

One thing to note is that, oddly, the game treats some shores as water, so player structures can not be built on some shores, let alone be built right against those shorelines. Therefore, it takes some effort to find a shore that allows building such an aforementioned enclosure.

Wave Zombie Spawn Points related to River
With my limited experience, I haven't seen spawn points in rivers. Maybe the devs did place some spawn points in river, or maybe not. Nonetheless, wave zombies cannot be spawned too close to their target. Since a river shore base is right next to the river, even if there are spawn points in rivers, they cannot spawn wave zombies because of being too close (same logic for sea shore base).

Regardless, with the understanding of the zombie pathing when their target is on land, if the aforementioned player structures (the enclosure with walls on 3 sides and a shoreline on the 4th side) is on one side of a river, then zombies that are spawned on the other side of the river "might or might not" cross the river to the shoreline that forms the 4th side of the enclosure. To explain this, it involves the theory of pathing limit.

The theory is that, a zombie always has 2 paths in mind towards their target - one being a point-to-point straight path regardless of any obstacles (i.e. even when there is an obstacle blocking this straight path, the zombie will still follow the path and head into that obstacle), and the other path being a meandering path where the zombie will go around obstacles. A zombie can choose only one of the 2 paths by comparing the length difference of those 2 paths against a constant threshold value defined by the devs in order to see if the meandering path is considered "too long." If the result says that the meandering path is too long, then the zombie will take the point-to-point straight path.

Since the player target is on land, the zombies will treat the 3D water entity (the river in this case) as an obstacle, as explained in the Pathing section, then there are 2 paths for the zombie that's spawned on the opposite side of the river where the player target is - one being the straight path towards the player target by travelling on the riverbed across the river (i.e. through the obstacle that is the water, because zombies cannot get stuck in water as stated in the beginning of the article), the other path being a meandering path that goes around the river by firstly, going to the land area near the source of the river, and then turning around to the other side of the river where the player target is.

With the understanding of pathing limit, if the meandering path is too long, then the zombie that's spawned on the opposite side of the river will take the straight path by crossing the river. That's why I said that zombies "might or might not" cross the river.

Nonetheless, I have no idea what the threshold value defined by devs for pathing limit is, because the tool for finding that value (Bait Trap) had been nerfed into almost uselessness for assisting tests. I only have an inaccurate ballpark estimation - a number somewhere between 40 to 60 Foundations (400 to 600 units) for v2.1.3.16. Again, this is an inaccurate estimation so treat it with a grain of salt.

Player on Platform above Water
This is related to the base you described in the Forest - a platform extended out towards the water.

As stated before, when zombies' target is unreachable, they will switch targets to a nearby player structure. If that player structure is unreachable, they will try to stay as close of it as possible.

That means, in the case of the aforementioned enclosure (walls on 3 sides and shoreline on the 4th side), with the platform that's extended out to the water (above water because they're not allowed to be built in water), the zombies will position themselves underneath that platform because this enclosure has no opening (water is deemed as an obstacle by zombies) and thus the player target on the platform becomes unreachable, i.e. the zombies will switch targets to a nearby player structure, which unfortunately, could be unreachable platform where the player is standing on.

That is, the zombies will now try to stay as close as possible to that unreachable platform. This causes them to enter into water for that platform. As stated at the beginning of this article, zombies cannot get stuck inside water. The result is that, for zombies that are in water, the shoreline that was once considered a natural barrier, protected by the obstacle that is the water, can now be breached. Those zombies that are in water underneath that platform will then plot a path from water (where they currently are) towards the shoreline, enter that enclosure, and go up to the platform where the player is.

In other words, if a platform that's extended out towards water is included as part of the base design, in order to be safe, do NOT use the shoreline as the 4th side of the enclosure (technically speaking, it's the water that is the obstacle that forms the 4th side of the enclosure) - instead, use real walls on that 4th side.

Or better yet, design a base that has an opening, i.e. the player is always reachable so that zombies will path through that player-designated opening and then gets greeted by melee traps. That is, adopt a base design with the player target being reachable, instead of the design with player target being unreachable, which is used by most ppl in The Forest. Night of the Dead has physics traps that can loop zombies' pathing by knocking them down to the ground level, forcing zombies to restart from the beginning of the path again and again ad nausea.

Unrelated Topic - Boat Base
Because zombies travel on the bottom of the sea, a boat base out at the sea will have wave zombies staying underneath the boat, a result of both the player being unreachable, floating above the seafloor, and the seafloor spot below the unreachable player being the closest.

Those underwater zombies can be killed by ranged traps that are built on "wings" (long platform extended outward away from the boat) and are aiming at the area below the boat.

Ranged traps have downward pitch limits (some have around 20 degrees and some around 40 degrees). For zombies that stay far below under the boat, the "wings" on which those traps are placed, have to be extended much further away from the boat so that those zombies are within the downward pitch limit, aka viewing angle, of those ranged traps.

In short, a boat base is another form of the base design where the target is unreachable (floating or underground). Recently, there is an undocumented change - items dropped in water will float (teleport) to the surface of the water. That is, there is no more worry of missing out loot from dead underwater zombies, and boat base is now viable.

Summery
If you use sea shoreline (not estuary) as a natural barrier, and all zombies targets (players) are on land (not at the sea), as long as no players get close to those 2 corners where the shoreline meet the player's walls, that base would be safe and also would not have zombies from the sea.

If you use river shoreline as a natural barrier, due to pathing limit, that base might be unsafe, especially when the base's far away from the source of the river, because the zombie's meandering path from the other side of the river, to the source of the river, and then to the player's side of the river would be too long (longer than the straight path by a distance which exceeds the threshold value of some number that's estimated to be between 400~600 units), causing the zombie to take the straight path across the river.

So, to save the trouble, don't use shorelines as a natural barrier. Better yet, adopt a base design with the player being reachable and with loopers.

[Evangelion]

Thanks, we did make a base on the beach not long after I posted this question, it's a lake (?) beach under the military base that's near the starting point. The entirety of the base is on land with walls going slightly over the water (at least far enough that you have to swim to pass it).

It's open on that side (didn't fully wall it above the water), and it is also open at the front, the walls make a sort of a choke point/killzone. So far (like 3 or 4 nights - from night 7), they always spawned on land and were coming to our base from the land, kind of from the sides and congregating near the land entrance, few miniguns and some spike traps on the opening + wood/metal pikes at the walls were enough to keep them easily obliterated.

So it can work I guess with no issues (and no zeds getting stuck in water) if done this way.