Thanks guys for the very good advices!

Here, I tried to take everything into account...
Click image for larger version. 

Name:	Sunken Temple- damaged.png 
Views:	382 
Size:	1.62 MB 
ID:	49259


The central water pool is needed as the Sahuagin reinforcement will come from there (it connects to the deeper sea and, when the temple was active it was used for propitiatory sacrifices).

The place is mostly neutral, it used to be the temple of a neutral divinity of nature and, when the humans move away, the Sahuagins move in. Still, these creatures are not all that evil. Violent and cruel, to be sure, but not metaphysically evil as demons would be...