`find the deepest point

clear all
clear

read fv.gf

he 5
tr 3
dr 6

vari dd
vari sdepth={depth}

macro change_depth
 de *+%1
 if {wpa}<>0 then exit
 exit change_depth %1
/

de -{sdepth} `initialize above waterplane
.change_depth 0.01 `depth increment, smaller is more accurate

set dd={sdepth} MINUS {depth}

\\ The deepest point is {6}{dd:2} {LUNIT} {7}below the waterplane. \
 \