Despite weighing 1,300–1,800 kg, hippos have surprisingly little subcutaneous fat compared to many large mammals. Instead of thick blubber (like marine mammals), most of their mass comes from dense muscle, heavy bones, and thick skin (~5 cm in places). That matters because: • Fat is buoyant (it helps animals float) • Muscle and bone are denser than water • Hippos lack large air-filled adaptations seen in strong swimmers So hippos don’t really swim. They walk, push, and gallop along riverbeds, using the ground to propel themselves. They can hold their breath for ~3–5 minutes and reflexively surface without waking up. Their body design is built for semi-aquatic stability, not hydrodynamic efficiency. Biomechanics breakdown: • Limb bones are columnar and weight-bearing → optimized for land support • Feet splay to increase contact area in mud • High bone density reduces buoyancy and stabilizes them underwater • Barrel-shaped torso = high mass, low drag stability in shallow water ...