Knot (UK) to Velocity of Sound in Pure Water

The UK knot is a historical variation of the knot based on the British nautical mile (6,080 feet) rather than the international nautical mile (6,076.12 feet).

1 UK knot ≈ 1.853184 km/h = 0.5148 m/s. Slightly faster than the international knot (1.852 km/h).

To international knots: × 1.00064. To km/h: × 1.853. To m/s: × 0.5148.

None in modern use. Only relevant for interpreting historical British naval records.

The difference between UK and international knots is only 0.064% — barely noticeable but important for precise navigation.

Assuming all old British ship logs use the same knot as today — they don't, but the difference is tiny.

Historical only. Effectively identical to modern knot. Only matters for historical maritime research.

The speed of sound in pure water at 20°C is approximately 1,482.7 m/s, significantly faster than in air due to water's higher density and bulk modulus.

Depends on water temperature, salinity, and pressure. At 20°C, pure water: ~1,483 m/s. Varies with depth and location.

To km/h: × 3.6. To ft/s: × 3.281. 1,483 m/s = 5,339 km/h = 3,317 mph.

Sonar (submarine detection, fish finding), ultrasound imaging, underwater communication, and oceanographic measurements.

Sound in water travels ~4.3× faster than in air. Whales can communicate over hundreds of km using this. SOFAR channel enables even longer distances.

Assuming sound speed in water equals sound in air — it's much faster. Also, forgetting temperature dependence.

~1,500 m/s in water (rule of thumb). 4–5× faster than in air. Increases with temperature, salinity, and depth.