. "''Hydra''-class sloop" . . "''Hydra''-class" . "''Hydra'' class" . . . "HMS ''Hecla''" . . "16.668" . . . . . . "Hydra-class sloop" . . "50.292" . "her class" . "Hydra-class sloop" . "9.7536" . "Hydra class" .