The A's want to build their ballpark and mall village on low-lying land in Fremont, less than half a mile from a tidal channel. With ocean levels expected to rise as the globe heats up, the high tides that churn up that channel could turn the A's ballpark into prime waterfront property -- or into soup. "You are talking about a meter rise of the sea level by the end of the century (around the bay),'' said Will Travis, executive director of the Bay Conservation and Development Commission, which helps regulate shoreline construction.