I too only use 64x when near land, as I've been taken by surprise by gradually shoaling bottoms at high TC, and lost the boat before I even knew I'd run aground.
I also never use the 'Kiel Canal In/Out' buttons, prefering to set my own waypoints, go at 64x (1 hour every minute - it only takes 7-10 minutes to get through) and when I near my last waypoint I go to 1x, set new points for a few miles, and enjoy the scenery for a minute or two before going back to TC. It makes the game much more believable and enjoyable - for me at least.
