This document specifies the following semi-quantitative methods for the assessment of transparency of waters: a) measurement of visual range using the transparency testing tube (applicable to transparent and slightly cloudy water), see Clause 4; b) measurement of visual range in the upper water layers using the transparency testing disc (especially applicable to surface, bathing water, waste water and often used in marine monitoring), see 5.1; c) measurement of visibility by divers in a destined depth, see 5.2. NOTE The quantitative methods using optical turbidimeters or nephelometers are described in ISO 7027-1.