While I appreciate the diamond badge for the Low Altitude Cacher I do not really feel like I earned it. I have found the cache GC397JN, whose published coordinates are in Lake Wairarapa, a lake that is 2.5m deep, and less than 10m above sea level. And yet the cache is flagged at 944m below sea level.
I think there has been an earlier Q querying this, but those caches were out at sea and we did not realise how much error there was.
There is something wrong with the altitude data somewhere!