Turtle
The turtle's relationship with buoyancy exemplifies nature's talent for compromise. Unlike the rubber duck's single-minded commitment to flotation, the turtle must balance the competing demands of surface breathing, underwater hunting, and seafloor foraging. This has produced what marine biologists term 'dynamic buoyancy management' - the ability to adjust relative density through precise control of lung inflation, achieving what amounts to a biological ballast system.
Sea turtles maintain a slightly positive buoyancy when relaxed, requiring minimal effort to surface for respiration whilst expending energy to descend. This configuration proves optimal for creatures that must regularly access both atmospheric oxygen and benthic food sources. The leatherback turtle can adjust its buoyancy to descend beyond 1,200 metres, experiencing pressures that would crush less adaptable organisms, before returning to the surface with apparent nonchalance.
The turtle's buoyancy versatility, however, comes at a cost. Unable to achieve the effortless flotation of simpler objects, the turtle must continuously expend energy to maintain its position in the water column. A sleeping sea turtle will slowly sink, awakening to surface approximately every four to seven hours - a schedule that, whilst biologically elegant, would prove entirely inadequate for an eight-hour bathtime session.
Rubber Duck
The rubber duck's approach to buoyancy achieves what engineers term 'elegant simplicity' - or what cynics might call 'having only one job and doing it adequately.' With an average density of 0.24 grams per cubic centimetre (versus water's 1.0 g/cm³), the rubber duck achieves positive buoyancy without effort, thought, or biological complexity. It floats because it cannot conceive of doing otherwise.
The physics of rubber duck flotation deserve examination. The air cavity comprising approximately 78% of internal volume ensures that, under normal bathroom conditions, no force short of deliberate submersion can compromise the duck's surface position. Even when pushed underwater, the duck returns to flotation with what observers describe as 'irritating cheerfulness' - the rubber duck equivalent of refusing to stay down.
This absolute commitment to buoyancy has proven advantageous in oceanic contexts. The 28,800 rubber ducks released in the 1992 Pacific incident maintained flotation across decades and thousands of kilometres, with specimens remaining buoyant despite years of exposure to marine conditions. No turtle, regardless of longevity, could match this feat - after death, the turtle inevitably sinks, whilst the rubber duck bobs on, apparently immortal, until the plastic itself degrades.