  The article reflects the author's point of view on the disasters that
occurred with American atomic submarines Thresher and Scorpion in 1960th and
Indonesian diesel submarine Nanggala-420 in April 2021. A possible role of
giant internal waves in such tragic events is discussed. Parameters of
large-amplitude internal solitary waves, their shapes and speeds of propagation
are presented. The author's reconstruction of the disasters is given.
