Which to rivers are between this island?

Question

I went to this island and it was beautiful!!!!!! This island is located right between manhattan and Long island. It is called Roselvelt Island. I caught fish and I caught a crab. It was small. I took it home but it died. Is this river a brackish water, fresh water or is it salt water?

Here is the picture of the island

http://www.newyorksocialdiary.com/socialdiary/2006/12_11_06/images/P1200515.jpg

Answer 1

Roosevelt Island is located in the East River.  It seems to be brackish water.

Answer 2

the hudson, it's just one river and its freshwater

Answer 3

The East River contains brackish water.  Roosevelt Island is in the middle of the East River.  One river only.