Difficulty using buoyancy plugin (libBuoyancyPlugin.so) for my gazebo model(for ROS1) - plugins

Question

RE-EDIT:
I want to apply bouyancy plugin my model which is made of 3 links. Do I need to apply the bouyancy plugin to all of the links for my model to float? Or do I just need to apply it to the base_link. The collision geometries for all of links are .dae files. But I have the gemotry of my base_link as a sphere for my Buoyancy plugin. Below is my .urdf.xacro file. For now, my model still phases through my world, so buoyancy isn't working. Not quite sure what I'm doing wrong.
<?xml version="1.0"?>
<robot xmlns:xacro="http://ros.org/wiki/xacro" name="wam-v">
<xacro:include filename="properties.urdf.xacro"/>
<link name="base_link">
<visual>
<geometry>
<mesh filename="package://freddy/mesh/WAM-V.dae"/>
</geometry>
</visual>
<collision name="base_link_collision">
<geometry>
<mesh filename="package://freddy/mesh/WAM-V.dae"/>
<!--sphere radius="1.5" /-->
</geometry>
</collision>
<inertial>
<mass value="247.07"/>
<inertia ixx="200" ixy="0.03" ixz="3.09" iyy="500" iyz="-0.05" izz="165.39"/>
<!--inertia ixx="198.828" ixy="0" ixz="0" iyy="198.828" iyz="0" izz="198.828"/-->
</inertial>
</link>
<joint name="base_link_joint" type="fixed">
<origin xyz="0 0 1.84"/>
<parent link="base_footprint"/>
<child link="base_link"/>
</joint>
<link name="base_footprint"/>
<link name="front_camera_link"/>
<joint name="front_camera_joint" type="fixed">
<origin xyz="1.2 0 0"/>
<parent link="base_link"/>
<child link="front_camera_link"/>
</joint>
<link name="left_camera_link"/>
<joint name="left_camera_joint" type="fixed">
<origin xyz="0 0.5 0" rpy="0 0 ${pi/2}"/>
<parent link="base_link"/>
<child link="left_camera_link"/>
</joint>
<link name="right_camera_link"/>
<joint name="right_camera_joint" type="fixed">
<origin xyz="0 -0.5 0" rpy="0 0 ${-pi/2}"/>
<parent link="base_link"/>
<child link="right_camera_link"/>
</joint>
<link name="rear_camera_link"/>
<joint name="rear_camera_joint" type="fixed">
<origin xyz="-0.5 0 0" rpy="0 0 ${pi}"/>
<parent link="base_link"/>
<child link="rear_camera_link"/>
</joint>
<link name="scan"/>
<joint name="scan_joint" type="fixed">
<origin xyz="1.5 0 -1" rpy="0 0 0"/>
<parent link="base_link"/>
<child link="scan"/>
</joint>
<link name="right_motor">
<visual>
<geometry>
<mesh filename="package://freddy/mesh/PROPELLER.dae"/>
</geometry>
</visual>
<collision name="right_motor_collision">
<geometry>
<mesh filename="package://freddy/mesh/PROPELLER.dae"/>
</geometry>
</collision>
<inertial>
<mass value="0.01"/>
<inertia ixx="0.00086" ixy="0.00" ixz="0.00" iyy="0.00086" iyz="0.00" izz="0.0017"/>
</inertial>
</link>
<joint name="right_motor_joint" type="continuous">
<origin xyz="${motor_position_x} -${motor_position_y} ${motor_position_z}"/>
<parent link="base_link"/>
<child link="right_motor"/>
<limit effort="0.5293" velocity="100${pi}" />
</joint>
<link name="left_motor">
<visual>
<geometry>
<mesh filename="package://freddy/mesh/PROPELLER.dae"/>
</geometry>
</visual>
<collision name="left_motor_collision">
<geometry>
<mesh filename="package://freddy/mesh/PROPELLER.dae"/>
</geometry>
</collision>
<inertial>
<mass value="0.01"/>
<inertia ixx="0.00086" ixy="0.00" ixz="0.00" iyy="0.00086" iyz="0.00" izz="0.0017"/>
</inertial>
</link>
<joint name="left_motor_joint" type="continuous">
<origin xyz="${motor_position_x} ${motor_position_y} ${motor_position_z}"/>
<parent link="base_link"/>
<child link="left_motor"/>
<limit effort="0.5293" velocity="100${pi}" />
</joint>
<link name="gps"/>
<joint name="gps_joint" type="fixed">
<origin xyz="0.8 0 0"/>
<parent link="base_link"/>
<child link="gps"/>
</joint>
<transmission name="right_motor_trans">
<type>transmission_interface/SimpleTransmission</type>
<joint name="right_motor_joint">
<hardwareInterface>VelocityJointInterface</hardwareInterface>
</joint>
<actuator name="right_motor_actuator">
<hardwareInterface>VelocityJointInterface</hardwareInterface>
<mechanicalReduction>30</mechanicalReduction>
</actuator>
</transmission>
<transmission name="left_motor_trans">
<type>transmission_interface/SimpleTransmission</type>
<joint name="left_motor_joint">
<hardwareInterface>VelocityJointInterface</hardwareInterface>
</joint>
<actuator name="left_motor_actuator">
<hardwareInterface>VelocityJointInterface</hardwareInterface>
<mechanicalReduction>30</mechanicalReduction>
</actuator>
</transmission>
<!--gazebo>
<plugin name="differential_drive_controller" filename="libgazebo_ros_diff_drive.so">
<commandTopic>cmd_vel</commandTopic>
<odometryTopic>odom</odometryTopic>
<odometryFrame>odom</odometryFrame>
<odometrySource>world</odometrySource>
<publishOdomTF>true</publishOdomTF>
<robotBaseFrame>base_footprint</robotBaseFrame>
<publishWheelTF>false</publishWheelTF>
<publishTf>true</publishTf>
<publishWheelJointState>true</publishWheelJointState>
<legacyMode>false</legacyMode>
<updateRate>30</updateRate>
<leftJoint>left_motor_joint</leftJoint>
<rightJoint>right_motor_joint</rightJoint>
<wheelSeparation>2.054</wheelSeparation>
<wheelDiameter>0.098</wheelDiameter>
<wheelAcceleration>1</wheelAcceleration>
<wheelTorque>10</wheelTorque>
<rosDebugLevel>na</rosDebugLevel>
</plugin>
</gazebo-->
<gazebo reference="scan">
<plugin name="BuoyancyPlugin" filename="libBuoyancyPlugin.so">
<!--a viscous liquid -->
<fluid_density>1000</fluid_density>
<link name="base_link">
<center_of_volume>0 0 1.84</center_of_volume>
<volume>47.712</volume>
</link>
<geometry><sphere radius="2.25" /></geometry>
</plugin>
</gazebo>
<xacro:include filename="camera.urdf.xacro"/>
<xacro:camera prefix="front"/>
<xacro:camera prefix="right"/>
<xacro:camera prefix="left"/>
<xacro:camera prefix="rear"/>
<xacro:include filename="$(find velodyne_description)/urdf/VLP-16.urdf.xacro"/>
<VLP-16 parent="base_link" name="velodyne" topic="/velodyne_points">
<origin xyz="0.8 0 0.3" rpy="0 0 0" />
</VLP-16>
<gazebo reference="scan">
<material>Gazebo/Blue</material>
<turnGravityOff>false</turnGravityOff>
<sensor type="ray" name="scan_sensor">
<pose>0 0 0 0 0 0</pose>
<visualize>false</visualize>
<update_rate>40</update_rate>
<ray>
<scan>
<horizontal>
<samples>720</samples>
<resolution>1</resolution>
<min_angle>-1.570796</min_angle>
<max_angle>1.570796</max_angle>
</horizontal>
</scan>
<range>
<min>1</min>
<max>30.0</max>
<resolution>0.001</resolution>
</range>
</ray>
<plugin name="gazebo_ros_head_hokuyo_controller" filename="libgazebo_ros_laser.so">
<topicName>/scan</topicName>
<frameName>scan</frameName>
</plugin>
</sensor>
</gazebo>
<gazebo reference="front_camera_link">
<sensor type="camera" name="front">
<update_rate>30.0</update_rate>
<!--camera name="head"-->
<horizontal_fov>1.3962634</horizontal_fov>
<image>
<width>800</width>
<height>800</height>
<format>R8G8B8</format>
</image>
<clip>
<near>0.02</near>
<far>300</far>
</clip>
<noise>
<type>gaussian</type>
<!-- Noise is sampled independently per pixel on each frame.
That pixel's noise value is added to each of its color
channels, which at that point lie in the range [0,1].-->
<mean>0.0</mean>
<stddev>0.007</stddev>
</noise>
<!--/camera-->
<plugin name="camera_controller" filename="libgazebo_ros_camera.so">
<alwaysOn>true</alwaysOn>
<updateRate>0.0</updateRate>
<cameraName>wam_v/front</cameraName>
<imageTopicName>image_raw</imageTopicName>
<cameraInfoTopicName>camera_info</cameraInfoTopicName>
<frameName>front_camera_link</frameName>
<hackBaseline>0.07</hackBaseline>
<distortionK1>0.0</distortionK1>
<distortionK2>0.0</distortionK2>
<distortionK3>0.0</distortionK3>
<distortionT1>0.0</distortionT1>
<distortionT2>0.0</distortionT2>
</plugin>
</sensor>
</gazebo>
<gazebo reference="right_camera_link">
<sensor type="camera" name="right">
<update_rate>30.0</update_rate>
<!--camera name="head"-->
<horizontal_fov>1.3962634</horizontal_fov>
<image>
<width>800</width>
<height>800</height>
<format>R8G8B8</format>
</image>
<clip>
<near>0.02</near>
<far>300</far>
</clip>
<noise>
<type>gaussian</type>
<!-- Noise is sampled independently per pixel on each frame.
That pixel's noise value is added to each of its color
channels, which at that point lie in the range [0,1].-->
<mean>0.0</mean>
<stddev>0.007</stddev>
</noise>
<!--/camera-->
<plugin name="camera_controller" filename="libgazebo_ros_camera.so">
<alwaysOn>true</alwaysOn>
<updateRate>0.0</updateRate>
<cameraName>wam_v/right</cameraName>
<imageTopicName>image_raw</imageTopicName>
<cameraInfoTopicName>camera_info</cameraInfoTopicName>
<frameName>right_camera_link</frameName>
<hackBaseline>0.07</hackBaseline>
<distortionK1>0.0</distortionK1>
<distortionK2>0.0</distortionK2>
<distortionK3>0.0</distortionK3>
<distortionT1>0.0</distortionT1>
<distortionT2>0.0</distortionT2>
</plugin>
</sensor>
</gazebo>
<gazebo reference="left_camera_link">
<sensor type="camera" name="left">
<update_rate>30.0</update_rate>
<!--camera name="head"-->
<horizontal_fov>1.3962634</horizontal_fov>
<image>
<width>800</width>
<height>800</height>
<format>R8G8B8</format>
</image>
<clip>
<near>0.02</near>
<far>300</far>
</clip>
<noise>
<type>gaussian</type>
<!-- Noise is sampled independently per pixel on each frame.
That pixel's noise value is added to each of its color
channels, which at that point lie in the range [0,1].-->
<mean>0.0</mean>
<stddev>0.007</stddev>
</noise>
<!--/camera-->
<plugin name="camera_controller" filename="libgazebo_ros_camera.so">
<alwaysOn>true</alwaysOn>
<updateRate>0.0</updateRate>
<cameraName>wam_v/left</cameraName>
<imageTopicName>image_raw</imageTopicName>
<cameraInfoTopicName>camera_info</cameraInfoTopicName>
<frameName>left_camera_link</frameName>
<hackBaseline>0.07</hackBaseline>
<distortionK1>0.0</distortionK1>
<distortionK2>0.0</distortionK2>
<distortionK3>0.0</distortionK3>
<distortionT1>0.0</distortionT1>
<distortionT2>0.0</distortionT2>
</plugin>
</sensor>
</gazebo>
<gazebo reference="rear_camera_link">
<sensor type="camera" name="rear">
<update_rate>30.0</update_rate>
<!--camera name="head"-->
<horizontal_fov>1.3962634</horizontal_fov>
<image>
<width>800</width>
<height>800</height>
<format>R8G8B8</format>
</image>
<clip>
<near>0.02</near>
<far>300</far>
</clip>
<noise>
<type>gaussian</type>
<!-- Noise is sampled independently per pixel on each frame.
That pixel's noise value is added to each of its color
channels, which at that point lie in the range [0,1].-->
<mean>0.0</mean>
<stddev>0.007</stddev>
</noise>
<!--/camera-->
<plugin name="camera_controller" filename="libgazebo_ros_camera.so">
<alwaysOn>true</alwaysOn>
<updateRate>0.0</updateRate>
<cameraName>wam_v/rear</cameraName>
<imageTopicName>image_raw</imageTopicName>
<cameraInfoTopicName>camera_info</cameraInfoTopicName>
<frameName>back_camera_link</frameName>
<hackBaseline>0.07</hackBaseline>
<distortionK1>0.0</distortionK1>
<distortionK2>0.0</distortionK2>
<distortionK3>0.0</distortionK3>
<distortionT1>0.0</distortionT1>
<distortionT2>0.0</distortionT2>
</plugin>
</sensor>
</gazebo>
</robot>