The open_water.zip file you have requested: Maps / Multiplayer / Open Water - 440.32kb is not available. Perhaps try browsing all files for the game Battle for Middle-earth II and upload any files you want to share or are missing. This is the only information we could locate:
4 player water map. Four islands at each corner with plenty of Outposts and space for farms etc. Two docks on each island and plenty of open water for sea battles. My second map and I never got to test it fully. Unfortunately this map taught me why theres no good water maps in the official BFME2 maps - AI won't use the water from what I've seen. Unfortunately this means this can only be played by human players online, but I thought it was worth uploading incase anyone did want to use it for that, please add comments if you do and tell me if it works or not.