It's called a "reflecting water glass" and it was designed by Jacob Reighard
(the "father of fishwatching") in 1908.
"The observer may thus stand upright in the water," Reighard wrote, "holding
the water glass in front of him, and by looking into the upper mirror see
submerged objects as he would see them if his head were beneath the
surface."
Don't know if any are commercially available, but a handy person should be
able to construct one. Reighard's 1909 paper -- "Methods of Studying the
Habits of Fishes, with an Account of the Breeding Habits of the Horned
Dace," Bull. Bur. Fish. -- included a diagram.
A summary of Reighard's fishwatching techniques is scheduled for the Winter
2002 American Currents.
Christopher Scharpf
Baltimore
/-----------------------------------------------------------------------------
/"Unless stated otherwise, comments made on this list do not necessarily
/ reflect the beliefs or goals of the North American Native Fishes
/ Association"
/ This is the discussion list of the North American Native Fishes Association
/ nanfa_at_aquaria.net. To subscribe, unsubscribe, or get help, send the word
/ subscribe, unsubscribe, or help in the body (not subject) of an email to
/ nanfa-request_at_aquaria.net. For a digest version, send the command to
/ nanfa-digest-request_at_aquaria.net instead.
/ For more information about NANFA, visit our web page, http://www.nanfa.org