This document specifies requirements, and provides recommendations and guidelines for marine soil investigations regarding: a) objectives, planning and execution of marine soil investigations; b) deployment of investigation equipment; c) drilling and logging; d) in situ testing; e) sampling; f) laboratory testing; g) reporting. Soil type references throughout this document follow the ISO 14688-1:2017 and ISO 14688-2:2017 definitions. Rock materials are only covered by this document to the extent that marine soil investigation tools can be used, e.g. for chalk, calcareous soils, cemented soils or similar soft rock. Hard rock investigations are not covered by this document. NOTE 1 Clause D.13 provides guidance. Foundation design is not covered by this document. NOTE 2 ISO 19901-4 and the respective design standards for the specific types of offshore structures as listed in the Foreword cover foundation design. The results from marine geophysical investigations are, when available and where appropriate, used for planning, optimization and interpretation of marine soil investigations. This document neither covers the planning, execution and interpretation of marine geophysical investigations nor the planning and scope of geohazard assessment studies, only the corresponding marine soil investigations aspects thereof. NOTE 3 ISO 19901-10 covers the planning, execution and interpretation of marine geophysical investigations. This document provides requirements and guidance for obtaining measured values and derived values. This document excludes requirements and guidance for determination of design and representative values. This document is intended for clients, soil investigation contractors, designers, installation contractors, geotechnical laboratories and public and regulatory authorities concerned with marine soil investigations for any type of offshore structures, or geohazard assessment studies.