- provided at sea by measurements taken by appropriate devices (instruments), such as, for example a CTD  to record to record depth, temperature, salinity and other parameters of the water column; those measurements are taken during expeditions (cruises) on board research vessels;

- obtained in the laboratory: a fluorometer to measure fluorescence of water and sediment samples (=an indicator of plant biomass);

- obtained from space by remote sensors mounted on satellites;

Observations can be also taken directly using underwater photography / video; such observations, to serve a scientific purpose, have to be quantified (for example, organisms seen in images are identified and counted).

Data for scientific studies are also provided by taking (with special devices) and analysing samples of seawater  and bottom sediment.

The samples are subsequently processed, examined and analysed in the laboratory.

Another type of observational data is provided by observations of live organisms kept in the laboratory (for example algal cultures) or of organisms kept in captivity, for example dolphins or large fish in aquaria.

Data can be provided by experiments which involve, basically, setting up a situation, be it in the field or in the laboratory, in which we control certain factors (change them) to find answers to questions we find interesting. Examples of questions asked of a field experiment are: how will storage of liquid carbon dioxide at the deep-sea floor affect the biota? How will the mining of polymetallic nodules (potato-shaped fragments of metallic ore forming a dense seabed cover in some very deep areas of the Pacific and Atlantic Oceans) affect the environment and biota? Experiments to find answers to these questions were run in the field (at sea).

Examples of questions asked of laboratory experiment include: how will physical disturbance and organic enrichment affect the sediment-dwelling fauna? Photos 9 and 10, taken at the Plymouth Marine Laboratory, Plymouth, UK show containers filled with sediment collected at sea in which smaller enclosures are experimental treatments – the sediment in them was either physically disturbed or enriched with organic material.