Swimming hydrodynamics simulator. Four stroke styles are modelled using a thrust-drag ODE: m·dv/dt = F_thrust(t) − F_drag(v) where F_thrust oscillates with the stroke cycle and F_drag = ½·ρ_water·Cd·A·v². Each stroke has a different frontal area, drag coefficient, peak thrust and stroke rate. The terminal (steady-state) velocity is reached when average thrust equals average drag. Front crawl is fastest due to its low drag area and continuous thrust profile. Breaststroke has the highest drag and lowest efficiency. An external streamlining slider scales all Cd values, modelling tech-suit effect.