A piece of driftwood suspended so that it was out of the water would work. But it needs a place to be out of the water for a bit on some sort of perch.
Also needs way to get up to said perch too so keep that in mind.
I have planted bamboo that is 18" and my crabs (Patriots) have been in there for 4 months without issue. They are cool.
Oh and btw Bamboo does very well in the aquarium if the leaves extend out of the water.