The Terra Moderate Resolution Imaging Spectroradiometer (MODIS) Land Water Mask (MOD44W) Version 6.1 data product provides a global map of surface water at 250 meter (m) spatial resolution. The data are available annually from 2000 to present. MOD44W Version 6.1 is derived using a decision tree classifier trained with MODIS data and validated with the Version 5 MOD44W data product. A series of masks are applied to address known issues caused by terrain shadow, burn scars, cloudiness, or ice cover in oceans. Version 6.1 is the generation of a time series rather than a simple static representation of water, given that water bodies fluctuate in size and ___location over time due to both natural and anthropogenic causes. Provided in each MOD44W Version 6.1 Hierarchical Data Format 4 (HDF4) file are layers for land water mask and water body classification. A quality assurance (QA) layer provides users with information on the determination of water. The new seven class water classification layer provides values for shallow ocean, land, shoreline, inland water, ephemeral water, deep inland water, moderate ocean, deep ocean, and a classification deemed to fall outside of the projection.Known Issues The seven_class SDS layer legend for classes 4 and 5 are incorrectly listed as Deep Inland Water and Ephemeral Water in the data for the entire mission period. Users are requested to follow the legend provided in the User Guide. For complete information about known issues please refer to the MODIS/VIIRS Land Quality Assessment website.Improvements/Changes from Previous Versions Additional data files will be produced annually and are scheduled for distribution in the first quarter of the calendar year. * Seven-class water body classification layer produced at 250 meter resolution is provided in tiled format. For Collection 6.1 and beyond, Antarctica data are now being produced.