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Migrate - Diel Vertical Migration for Subnautica

I adore Subnautica but something that's always bothered me about it is that once you come to learn the patterns and locations of all the creatures it can come to feel a bit...sterile. The creatures that matter are all roughly where you'd expect them to be when you expect them to be there and the surface of the ocean is practically always safe.

Migrate is the first in several mods I've been working on aimed at precisely this issue.

Here on Earth the biggest single migration on the planet happens at night. Smaller creatures near the bottom of the food chain migrate up from the deep dark below to feed on the abundance of life taking advantage of the sunlight near the surface to grow. The migration of these creatures is so vast that scientists taking some of the first ever sonar readings mistook the sheer wall of organisms rising from the depths for the ocean floor itself in a phenomenon known as the "Deep Scattering Layer". This migration is known as "Diel Nocturnal Migration" but other forms of Diel Migration include organisms that sink to the ocean floor at night only to rise back up at day as well as organisms that make a trip twice daily during the twilight hours of sunrise and sunset.

My intent with this mod is to start to bring back some of the surprise and excitement many of us seem to lose as we play and so on that note it may be preferrable to you to jump into this mod blind. If that's the case I recommend you stop reading here as I'll explain the basic mechanics of the mod as they stand below.


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Mod Spoilers Below
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Migratory Patterns
While there are many different types of vertical migration, this mod focuses specifically on the 3 forms of Diel Vertical Migration (also known as Diurnal Vertical Migration). These were briefly touched on above but to resummarize the forms of Diel Migration as they apply to this mod go as follows;

- Nocturnal: These creatures live in the depths during the day, but come to the surface as darkness falls to feed (yes, this DOES include during eclipses).

- Reverse: These creatures prefer to remain at the surface, basking in the sun during the day and sinking down during the dark hours to avoid the nocturnal crowd.

- Twilight: These creatures make two seperate ascents during the day, one as the sun is rising and one as the sun is setting. At the moment I expect the most issues with these as in terms of subnautica this is quite the rapid rise/fall for creatures to make.


Food Cycle Distribution
There are many other levels of the food chain besides predator and prey but I've narrowed all the migratory creatures down into three food chain categories that should respond differently to migration. They go as follows;

- Prey: These are the first ones to the surface during any migration and the first ones back down. The smallest creatures and filter feeders should surface to feed on zooplankton and other sun dependent microorganisms and the larger predators should surface to feed on them.

- Predators: These will attempt to follow prey on their migratory paths according to size distribution. Smaller predators should make their way after Peepers and other small feed fish and the larger predators should follow after that.

- Other: These are lifeforms outside the narrow bounds of prey and predator. In terms of this mod they mostly consist of peaceful leviathans that act as neither predator nor prey. They just kinda do their own thing. I have migratory patterns set for a few but... Idk I needed an outlier category. .-. 


Biomes and Distribution
As of the current release I have not changed the distribution of creatures at all. I likely will end up doing this in the future as deeper zones with a larger water column might otherwise seem "thinned out" in terms of creatures. 

This mod currently only applies to creatures in the following surface biomes:

- The Bulb Zone
- The Mountains
- The Grand Reef
- The Sea Treader Path
- The Dunes
- The Blood Kelp Zones (only the surface areas- not the caves!!!)
- The Grassy Plateaus
- The Sparse Reef
- Creepvine Forests

None of the canon migratory paths have been added for creatures in the lost river (ghost leviathans/dragon leviathans making their way in and out) but functionality for that is currently being planned and worked on for Wander, my next mod in this little series of changes.


AI and Creature Behavior
I really tried not to mess with this as much as possible. The intent of Migrate is not to alter the way any creatures interact with their environment, but just rather to change from where in the water column they make those interactions. Creatures that are frequently tied to behaviors that preclude vertical migration (aka Bonesharks) have not had any changes made to them

Creatures currently affected by this mod and their schedules go as follows;

Nocturnal Migration
(Predators)
-Ghost Leviathan
-Reaper Leviathan
-Amp Eel
-Biter

(Prey)
-Peeper
-Oculus
-Bladderfish
-Eyeye
-Spadefish


Diurnal Migration
(Prey)
-GarryFish
-Holefish
-Reginald

(Other)
-Reefback


Twilight Migration
(Predator)
-Sandshark