longitudinal member 32 the resilient member 84 then extends inwardly towards the pipeline p and is received by each one of the upper arms 76 and 80 at pivot points 89 the amount of pressure provided by the rollers 26 and 28 upon the pipe p may be simply adjusted in accordance with the pipe diameter or other purposes by simply adjusting the hydraulic fluid pressure applied to the resilient member 84 in any conventional manner as by hoses 85 in which the hydraulics are controlled on the water surface also pressure gauges or other pressure sensitive means may be incorporated in the shock absorber to detect pressure variations to not only maintain the desired pressure of the rollers on the pipeline but also to detect obstructions on the surface of the pipeline for example anodes etc that the present trenching apparatus should if the obstructions are minor override thus by the rollers 26 and 28 being in controlled pressured contact with the pipeline p any curvature of the pipeline will be followed by the rollers and therefore the trenching apparatus as it proceeds down the pipeline the sole propulsion for the trenching apparatus is a thruster assembly 24 as best shown in fig4 this thruster assembly has a number of individual thrusters preferably as shown three in number 24 p on the port side 24 s on the starboard side and 24 c centrally located on the longitudinal axis of the.