Network Simulator in Linux: NS release 2.35, NS Manual (pdf), http://www.isi.edu/nsnam/ns
GNUplot (Software to plot graph in Linux): GNUplot Download, Gnuplot Manual (pdf), www.gnuplot.info
Aqua-Sim-1.0: If you are searching for an underwater sensor network simulator than you can try "Aqua Sim". It is a NS 2 based simulator for Underwater Acoustic Sensor Networks in Linux. Installation guide and development tutorials area available in Link to Download. Installation Guide