Hydrodynamics and Evolution of Turtles

Turtles seem, at first glance, like unlikely swimmers. Encased in rigid shells that appear to defy the sleek streamlining we associate with aquatic life. Yet sea turtles glide across entire oceans with remarkable efficiency, while freshwater turtles manoeuvre deftly through rivers and ponds. How do these ancient reptiles make it work?

This talk dives into the surprising science of turtle hydrodynamics, revealing how evolution has shaped different species to exploit the physics of water in distinct ways. We will explore how sea turtles, such as the iconic green and leatherback turtles, have evolved wing-like flippers that generate lift-based propulsion, more akin to flying than traditional swimming. In contrast, many freshwater turtles rely on drag-based paddling, using their limbs in alternating strokes that favour control over speed.

At the centre of this story is the turtle shell, an evolutionary innovation that imposes constraints but also opens unexpected opportunities. We will examine how shell shape and body plan influence flow patterns, drag reduction, and energy efficiency. Why are sea turtles more streamlined than their terrestrial relatives? What trade-offs have turtles made over 200 million years of evolution to balance protection, mobility, and performance?

By comparing turtle species across habitats and evolutionary lineages, this talk reveals how a single body plan can be adapted to different hydrodynamic challenges. Along the way, we will connect these biological insights to broader principles in fluid dynamics and even modern engineering design. Blending evolutionary history with the physics of motion, this talk uncovers how turtles, often seen as slow and cumbersome, are in fact elegant solutions to one of nature’s greatest challenges.