For anyone else getting this far ... the 'oceanlevel' valye is constrained to values from 0.0 to 100.0 (float, basicaly a percentage).  That is, an 'oceanlevel' value of 0.0 represents the lowest ocean level for the current map (the default map level).  Whereas an'oceanlevel' value of 100.0 represents the maximum (highest) level for the current map.  Basically the maximum 'oceanlevel' is the value needed to completely cover the highest point on the current terrain.

Note also that none of the monuments currently take the 'oceanlevel' value into considerstion when rendered.  That is, caves and other underground areas on the map will NOT become 'flooded' as the ocean levels rise.  For example the cave under 'Oxums as Station' will always be open and NOT under water even thought other portions of the momument will are.