  Measurements of optical properties in media enclosing Cherenkov neutrino
telescopes are important not only at the moment of the selection of an adequate
site, but also for the continuous characterization of the medium as a function
of time. Over the two last decades, the Baikal collaboration has been measuring
the optical properties of the deep water in Lake Baikal (Siberia) where, since
April 1998, the neutrino telescope NT-200 is in operation. Measurements have
been made with custom devices. The NEMO Collaboration, aiming at the
construction of a km3 Cherenkov neutrino detector in the Mediterranean Sea, has
developed an experimental setup for the measurement of oceanographic and
optical properties of deep sea water. This setup is based on a commercial
transmissometer. During a joint campaign of the two collaborations in March and
April 2001, light absorption, scattering and attenuation in water have been
measured. The results are compatible with previous ones reported by the Baikal
Collaboration and show convincing agreement between the two experimental
techniques.
