Geotechnical surveys gather information about the physical characteristics of the soils and rocks that make up the seabed. These surveys are vital to the development of a project. For an offshore wind farm, geotechnical data will inform foundation design.

To collect geotechnical data, vibrocores and cone penetration tests (CPT) are usually carried out. The depth of these tests will vary depending upon the target depth of the activity.

As the name suggests, a vibrocore collects a core sample of the seabed sediment layers. Whilst during a CPT, a cone is pushed into the ground and multiple measurements are taken, including cone resistence and friction. Many geotechnical surveys will also carry out a piezocone test (CPTu), which tests for water pressure and can be important in understanding the engineering properties of the soil.