[Raymond S.]

I bought "star moss" once and of course it didn't work under water and I soon found threads that said most have
trouble growing it underwater. But then I started noticing it on top of the ground around the streams that I collect from.
So try it on the "dry" side. But it grows in damp soil.

 

[Raymond S.]

Not suggesting you buy from them/your choice, but it's just a list of plants that work in brackish water.
Just starting in plants so I can't verify which would grow above water.
http://www.aquariumplants.com/Brackish_Water_Plants_s/22.htm
Put your pointer on "Aquarium Plants" for pop out list to be sure of brackish type.