FloatableBody

Description

This is a simple physics system working on Godot Engine 4 that simulates the behavior of an object floating in a water-like fluid.

Create a scene with a FluidArea3D node to represent underwater and a FloatableBody3D node to represent a floating object.

Add a FluidArea3D node to the scene. This node inherits from Area3D, so add a CollisionShape3D to it as a child node and set the shape. I recommend adding a MeshInstance3D to make it visually compelling.
Add a FloatableBody3D node to the scene. This node inherits from RigidBody3D, so add a CollisionShape3D as a child node to it and set the shape.
Play the scene. The FloatableBody3D will fall down and enter the FluidArea3D and will be raised by buoyancy.

The above explanation is for 3D, but the procedure is the same for 2D.

Describes the parameters that are important for an FloatableBody3D/2D to float in water.

Density of FluidArea3D/2D.
- The more fluid density you increase, the more buoyant the object will be.
Mass of RigidBody3D/2D.
- The more you increase the object's mass, the less buoyant it will be.
Center of Mass of RigidBody3D/2D
- The center of gravity of an object affects its stability. A ship, for example, will move more naturally if its center of mass is lowered.
Volume (Size, Radius, Height) of Shape3D/2D of CollisionShape3D/2D
- The more you increase the volume of an object, the more buoyant it will be. Larger objects should be balanced by increasing their mass.
Fluid Damp of FloatableBody3D/2D.
- The more resistance you increase, the harder it will be for the object to move in the fluid. If the resistance is too small, the object will move unnaturally, so increase the resistance to stabilize the object.

For cases where you want to use buoyancy with CharacterBody3D/2D, use FluidInteractor3D/2D. This is the class used inside FloatableBody3D/2D.

There is FloatablePlayer3D/2D as a sample code. Please refer there for detailed usage.