Dear Stuart and Robert
You can indicate the depth using the "distance from reference surface" field available in the instrument form (data series--> deployment--> instrument). Negative distances can be specified. Do not forget to indicate the "type of reference surface" in the following field.
If for each depth a different instrument instance (manufacturer, model and serial number) is used please add as many deployments as needed and feel in the corresponding "distance from reference surface" and "type of reference surface".
If the same instrument instance (manufacturer, model and serial number) is used for different depths please indicate one depth in the "distance from reference surface" field and the others in the "comment" field (available at the bottom of the instrument form).
In the future OSCAR/Surface will allow to specify more than one height (or depth) for an instrument instance.
Cheers
Lucia