Is a 'slow' swimming pool impeding world records?

Original Article ↗ Hacker News Discussion ↗

Claims that the Paris 2024 Olympic pool is “slow” have prompted debate over how much pool design — especially depth, wall and gutter construction, and wave turbulence — can affect elite swimmers’ times and the likelihood of world records. Former competitors and coaches point to unusually shallow water, temporary construction in a rugby stadium, and choppier conditions in outer lanes, while others counter that CFD models, stricter standards, or factors like COVID prevalence and reduced doping could also explain slower performances. Many agree that conditions appear to be affecting everyone similarly in terms of medal fairness, but argue this Olympics may produce fewer record-breaking swims compared with past Games held in “faster” pools.

Physical factors behind “slow vs fast” pools

  • Many competitive swimmers assert that pools differ measurably in speed.
  • Two main factors cited:
    • Depth: Paris pool ~2.15 m/7 ft, shallower than the 3 m long recommended and below updated 2.5 m minimum; shallower water is said to cause more reflected turbulence.
    • Side design: whether water spills into deep gutters vs rebounds off walls, affecting surface chop, especially in outer lanes.
  • Observers note athletes visibly struggling in final meters compared with previous Olympics.

Depth, turbulence, and lane effects

  • Explanations offered:
    • Shallower depth means waves reach the bottom sooner and reflect back with more energy, increasing drag on legs/feet.
    • Deeper pools allow vortices to dissipate before returning to the surface.
  • Fast qualifiers get center lanes to reduce side-wall chop and benefit from drafting effects.
  • Outer lanes are often left empty in finals; slower swimmers are placed closer to walls.

Water properties, circulation, and equipment

  • Minor contributors discussed:
    • Water temperature, salinity, borates, and dissolved chemicals affecting viscosity, surface tension, buoyancy.
    • Pool recirculation systems must run continuously but are regulated to minimize currents.
    • Lane lines, gutters, starting blocks, touchpads, and even bottom-mounted cameras and lap counters can affect flow or perception.

Evidence vs intuition and modeling

  • Swimmers and coaches strongly believe depth matters; some argue their thousands of hours in pools give reliable intuition.
  • Others prioritize CFD and controlled studies, noting:
    • Models suggest diminishing returns beyond ~2 m.
    • It’s hard to isolate depth from other variables.
  • Debate over whether empirical “slow times” alone can identify depth as the cause.

Fairness, records, and venue design

  • Many say competition is fair if all swimmers face the same pool, even if records are less likely.
  • Others argue Olympic pools should be optimized for record potential, given the event’s importance and athletes’ short peak careers.
  • Paris used a temporary pool in a rugby arena to avoid a “white elephant,” constraining depth and sightlines.
  • Some call for stricter global standards or even permanent Olympic venues; others note variability is normal in many sports.

Alternative explanations and counterpoints

  • COVID infections among swimmers and broader viral circulation are raised as possible performance dampeners; extent is unclear.
  • Doping patterns are also mentioned, including speculation about reduced illicit enhancement vs prior cycles; claims are contested.
  • Generational shifts (e.g., some nations between star cohorts) may contribute.
  • The “slow pool” narrative is weakened but not entirely dismissed by several strong world records set in Paris, including a standout men’s 100 m freestyle.