Even iron can float.
An object floats when its average density is lower than the liquid's. Try mercury: its density is greater than iron's, so the iron ball rises to the surface. The duck's density includes the air inside it.
Buoyancy lab
Liquid Simulator
A cube of liquid, a few familiar objects, and one question: will they float? Change the liquid and watch the answer change.
10⁰ m · 60 cm (a cube of liquid) · Three.js · Buoyancy & liquid materials
Filling the liquid cube…
Slow is not the same as floating.
Thicker liquids resist motion. Turn up viscosity and drop the objects again: they take longer to settle, but their final floating or sinking outcome stays the same.
A small, invisible tank.
The walls and bottom hold the liquid in a 60 cm cube. Buoyancy uses displaced volume; drag slows each object. Surface tension changes the illustrative ripples. Objects move vertically in separate lanes, with no collisions or liquid-level rise. The duck uses a spherical buoyancy proxy.
Model references: Archimedes' principle · Mercury density. Presets are approximate room-temperature examples. Oil varies by composition. Surface ripples are illustrative, not a full fluid solver.