The present formal release prepared by the Marine Division of IMCA is mainly intended to provide required technical guidance detailing a working framework of competence assurance as well as the assessment for the personnel who are considered critical for safety and working for all organizations that are forming the IMCA. It has been prepared by the IMCA specialists on the basis of the numerous activity reports as well as relevant recommendations officially provided by several working groups. The publication is covering a truly wide range of positions within the marine, offshore and underwater engineering industries involved in serving the oil & gas exploration and production sector. The authors of the volume are planning to further expand the content of the present guidance to a wider range of competencies. This nice volume aims to clearly specify the minimum applicable standards as well as qualifications plus the minimum professional experience to ensure the personnel competency, and the assurance framework that shows how exactly the proficiency should be developed and demonstrated. The publication shall definitely be treated as an excellent reference paper that details the technical procedures, applicable criteria and recording system that should be implemented and further applied for proper assessing the competence of the "safety-critical" personnel.