Why does my Unreal Water Plugin BuoyancyComponent not float my object?

The actor's mesh must Simulate Physics, the water body needs collision enabled, and the BuoyancyComponent must have at least one Pontoon defined with valid local position and radius. Missing any one means no buoyancy force applies.

How do I add pontoons to a buoyancy component?

On the BuoyancyComponent, expand Buoyancy Data > Pontoons. Add entries with Relative Location at points around the bottom of your hull and Radius covering the volume each represents. More pontoons (4-8) produce smoother floating; fewer (1-2) is enough for small props.

Why does my object sink despite buoyancy being set up?

BuoyancyCoefficient may be too low or the object's mass is too high relative to volume. Increase BuoyancyCoefficient (default 1.0; try 1.5-3.0 for floating objects) or reduce mass via PhysicsAsset/SetMass.

Fix: Unreal Water Plugin Buoyancy Not Working

Quick answer: Object must have a SimulatePhysics-enabled root mesh, the water body needs collision, and the BuoyancyComponent needs at least one Pontoon. Tune BuoyancyCoefficient for floating strength.

Here is how to fix Unreal Water Plugin BuoyancyComponent that does not float objects on water. Three things must align: physics simulation, water collision, and pontoon placement.

The Symptom

Boat or floating prop sinks straight to the riverbed instead of floating. Buoyancy component is attached but the object is not affected.

What Causes This

SimulatePhysics off. Without physics, no force can be applied.

Water body collision off. The buoyancy component samples the water body collision; without it, no water is detected.

No pontoons. Pontoons define where buoyant force applies. Without them, there is no point of force application.

Coefficient too low. Default may not overcome gravity for heavy objects.

The Fix

Step 1: Enable physics on the floating mesh.

StaticMeshComponent:
  Simulate Physics       = true
  Mass (kg)              = 100
  Collision              = BlockAll

Step 2: Verify water body collision. On WaterBodyOcean / River / Lake, ensure CollisionEnabled is set to QueryOnly or QueryAndPhysics. The buoyancy component samples this volume.

Step 3: Add pontoons.

// On the BuoyancyComponent
BuoyancyData:
  Pontoons:
    - RelativeLocation: (100, 50, -20)   // front-right
      Radius:           30
    - RelativeLocation: (100, -50, -20)  // front-left
      Radius:           30
    - RelativeLocation: (-100, 50, -20)  // rear-right
      Radius:           30
    - RelativeLocation: (-100, -50, -20) // rear-left
      Radius:           30
  BuoyancyCoefficient:  1.5
  BuoyancyDamp:         0.1

Step 4: Tune coefficient. 1.0 = neutral buoyancy (sinks slowly). 1.5-2.0 floats. 3.0 bobs aggressively. Match to the look you want.

Step 5: Verify with show debug overlay. Use show CollisionPawn or the Buoyancy debug visualization (depending on plugin version) to see pontoon positions and submersion depth.

“Physics on, water collision on, pontoons placed, coefficient tuned. Floats reliably.”

Related Issues

For physics constraint after load, see Constraint After Load. For decal on translucent water, see Decal on Translucent.

Physics on. Water collision on. Pontoons placed. The boat floats.