Spectrum of the para H₂O 2₀₂−1₁₁ emission line towards SDP.17b, where the velocity scale is centred on its observed frequency at 298.93 GHz (corresponding to z = 2.3049). The rms noise is  ~4.7 mJy/beam in 31.6 MHz channels. A Gaussian fit to the H₂O spectrum is shown as a solid line while the dotted line shows the underlying dust continuum emission. The H₂O line is clearly asymmetric and not well fit by a Gaussian profile.