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 part 1 of ISO 7027.