From the MODIS (Moderate Resolution Imaging Spectrometer) UCSB Emissivity Library. Includes four sample for Water, three for Seawater, three for Ice and two for snow.

Commentary on the data on the site read, in part:

“Water, ice, and snow generally  have a high emissivity, 0.94 to 0.99, across the thermal infrared region. Snow is unusual in that it has a high reflectance in the solar (visible) region where most of the downwelling energy is during the day, and a very high emissivity in the thermal region.”