When calibrated to ITS-90, where one must interpolate between the defining points of gallium and indium, the boiling point of VSMOW water is about 10 mK less, about 99.974 °C. Source Wikipedia
Precise measurements show that the boiling point of VSMOW water under one standard atmosphere of pressure is actually 373.1339 K (99.9839 °C) when adhering strictly to the two-point definition of thermodynamic temperature. Source Wikipedia
Fun fact: The normal boiling point of water isn't exactly 100 °C (at least not since 2019 when the definition of the Kelvin scale was changed to use the Boltzmann constant and decoupled from the triple point of water)
