Frame-to-frame optical flow motion analysis dataset for Radix balthica trochophore embryos exposed to different combinations of temperature and salinity. Twenty five time points for each embryo are recorded with temperatures separated into individual .h5 result files. Original detail of the wet-lab study from which the video was taken can be found in the third experiment featured in this paper: https://doi.org/10.1371/journal.pbio.3000074. The motion analysis method used was a derivative of the method developed and validated in this paper: https://doi.org/10.1186/1471-2105-14-37.