Data are distances (in cm) to water measured by an experimental near-infrared lidar sensor in six different setups (2017–9). Laboratory tests conducted at Imperial College London include quantifying the effect of (i) distance, (ii) sensor inclination, (iii) turbidity/clarity of the water, and (iv) ambient temperature on measurement bias. Outdoor tests at three locations in London interrogated the effect of varying water surface roughness on the measurements. A dataset of high-frequency measurements is also included, from which the effects of sample autocorrelation were interrogated.