Ok, just make another water block, the same as the water surrounding the FOF, and then tag it the same as the FOF
This is the FOF over the water with a tag only used once.
(TAG 2) FOF-> .............................. __
(TAG 1) Water-> ----__----
Tag a water type, of the same height as the surrounding water, to the same as the FOF
(TAG 2) FOF-> .............................. __
(TAG 1) Water->-----------
........................................................................................................................ ^--The same tag as the FOF (2)
Thtas as much as i could do with a visual representation in ACII ^_~