Procedurally generate water around a procedurally generated map

Unity Engine
1

So I have been playing around with the idea of building a survival / crafting / rogue-like / etc top down 2D game in Unity3D and been building out very simple implementations of the core gameplay mechanics the past couple of weekends (character animation / movement / attacking, health / stamina system, inventory system, basic GUI for health / stamina / inventory, building / destroying structures, etc.). Now I am working on some basic procedural map generation. From what I have read, the easiest (maybe best for my needs) is to basically do multiple passes of using different noise generation to generate the different layers of my map. Currently I am doing one pass of simplex (using the FastNoise library from the assets store) to generate the basic ground map (dirt / sand, grass, dark grass / swamp) and so far pretty happy with it:

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The issue I am now facing is that I want to procedurally generated water surrounding this map to basically acts as a natural barrier to keep the user within this map (instead of just having a random point where the user can’t move). Noise generation does not seem like it would work for this since I need it to only be around the map (and be pretty thin but still have some “natural” looking form instead of just being a straight line type thing) and noise generation is random looking (even though noise it not really random as it is reproducible, it just looks random).

What would I have to do to achieve something like this (and any sort of details or explains of math if needed, which I would assume, would also be great because this type of math is not something I really know a lot about)?

2

Generate a similar map of ‘water’ blobs, and then combine them by allowing land to have priority over water pixels. ie let the water only be drawn in the mid-green areas.

3

@imaginaryhuman_1 The issue if that I am not looking to place random bodies of water in the map (I will probably use another noise generation to do that is another pass when generating the map), I want to have all 4 edges have water but have randomly looking coasts to act as “natural” barrier to keep the user in the map area (basically the map should look like 1 big island).

4

Maybe this will help:

Specifically the section about Islands.