Heavelock is a start-up company, located in Trondheim (Norway). We address a specific drilling industry challenge, namely downhole pressure variations caused by movement of the drill string in a well. Our hardware (TRL2 - pilot scale version tested) actively mitigates downhole pressure variations, caused by rig heave. Our software (available now) calculates surge & swab margin when tripping/pulling drill pipe or completion string and takes the influence of rig heave into consideration. Our surge & swab model is a very advanced transient model that takes into account elastic properties of the drill string, friction in the well, non-Newtonian character of drilling mud. It has been extensively verified using real field data.