IMU linear acceleration to linear Velocity

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Hi Im doing some UUV simulation in gazebo and have IMU that gives me 9DOF namely my data is

orientation: 
  x: 0.018933040808
  y: -0.00209639450915
  z: 0.337785931366
  w: -0.941030185311

angular_velocity: 
  x: -8.94731200724e-05
  y: 0.000117146098958
  z: 7.81746250685e-06

linear_acceleration: 
  x: 0.0865246576615
  y: -0.363323777859
  z: 9.79281330072

I would like to get the linear velocity and some how use the orientation for less error when do the double integration. I also have some 3D Pose sensor. So Its underwater robot simulation. I mean I have the IMU data for the orientation so some how want to incorporate that in my integration when get the velocity values. Any help?