To install software for the gazebo simulator please follow these steps:

sudo sh -c 'echo "deb http://packages.osrfoundation.org/gazebo/ubuntu trusty main" > /etc/apt/sources.list.d/gazebo-latest.list'
wget http://packages.osrfoundation.org/gazebo.key -O - | sudo apt-key add -
sudo aptitude update
sudo aptitude install robosub-simulator

Then clone the repo: https://github.com/PalouseRobosub/simulator_gazebo to your catkin workspace.