The dataset comprises of vertical profiles of water column properties (temperature, salinity, conductivity, pressure, depth, sound velocity and density) of the full water column in the South West region of the UK. Measurements were taken opportunistically at three main locations (L4, L5 and E1 Western Channel Observatory stations) as well from Plymouth Sound and the surrounding inshore areas. Data have been gathered using a Valeport MIDAS 606 CTD (with a passive flow induction cell, Platinum Resistance Thermometer and a strain gauge transducer) and extracted and processed using Valeport DataLogX2 software (version1.0.4.1270). The CTD was deployed using vertical deployment from the RV MBA Sepia and were hauled using a manually controlled hydraulic winch. The surveyors have been dependent on the sensor calibrations applied by the CTD manufacturer (Valeport). Manufacturer calibrations are applied to the in situ direct measurements via sensor specific microchips in the CTD unit. Derived parameters are calculated using the in-built processing provided with the units software: Datalogx2. The data have been collected in the framework of the long term monitoring of the Western Channel Observatory stations and the Plymouth inshore fisheries undertaken annually by the Marine Biological Association of the United Kingdom. The RV MBA Sepia department of the Institute carried out the data collection activities.