Buildings and Infantry.

[Mobhack]

And the DD Tanks have thier own specific classes - 134 DD tank and 135 Snorkel tank. Whether that leads to a specific snorkel graphic or not, you will need to experiment with. One may use a "snorkel" and the other a DD sherman graphic when in the water. Been a long time since I coded it, but thats probably it - Unit class X for a flotation tube and Y for a sherman with sides up swimming graphic.

There is no alternative "floating" icon, its all hard coded for the specific types. You would need to find the snort and DD icons wherever they reside and change for your purposes if you want to change them. (Similar hard-coded icon swaps are done for the parachutist types while falling out the back of a plane - the parachute icons are special ones)

Also IIRC, there is a difference in the to-hit and hit resolution for firing on a submerged snort tank and a floating DD tank. Neither react well to being hit by any weapon type (glug glug!) but the snort may be treated as a smaller target (likely also for spotting the thing), vaguely recalling code I wrote back in the MSDOS days and havent looked at since. I vaguely recall snipers being a good thing(tm) to shoot at snorts with for exmaple, but I am not going to delve into the code to refresh my mind.