I was thinking about how to keep track of this and decided to use two typs of shell splash markers, one with a single splash, one with two splashes so they are visually distinct.
The method I’ve been using is this:
Suppression incurred in the gunnery phase is denoted by placing a splash marker near the bow of the target vessel. (Heavy suppression = 2 splashes). At the end of the gunnery phase all splashes at the stern of vessels are removed.
In the movement phase, after each vessel moves, any splashes that were at the bow are placed near the stern.
I picked it up as the East African campaign always held some fascination (must have been too many viewings of the African Queen as a kid). I found a video on Utube about the “duel” between the gun boats dragged overland and the German ships on Lake Tanganyika.
There’s also a very good documentary on Prime Video called ‘The Real African Queen’. Well worth a watch.