You haven't seen too many screen savers that have 19 keyboard shortcuts, either.
But Marine Aquarium 3 isn't a "screen saver". It's a simulation of a marine aquarium.
That is why I phrased it the way I did - the screen saver capability of MA3 works pretty much just like other SS's do except it intercepts certain key strokes rather than have them stop the SS function as some may.
While running as an "app", it allows those same key strokes (or a mouse "right click"), to change what is displayed.
Regarding whether it is a screen saver or not, with the recent (through 11e) changes, what exactly doesn't it do to qualify as a screen saver? It appears to me it now meets all the perceived requirements to be a screen saver.