With hindsight there are two things that the KuK Marine could do that would actually matter in the big picture, rather than just shifting deck chairs on the Titanic
1) Set up a good naval intelligence Branch. If someone can catch Redl before he sells out the Austrian War plans to Russia, and from them to Serbia, you mitigate the disasters of 1914, which basically wins the war
2) Expand the River fleet, more monitors, bigger ones with longer ranged guns, more minesweepers, attached naval infantry. Being able to actually seize the Sava bridges on the first day of the war could possibly make the initial Serbian campaign do much better, and more floating artillery support might just move the needle enough that even if the first invasion of Serbia still goes broadly as OTL the third might succeed from additional accumulated losses degrading the Serbians just enough. If any one of the three invasions of Serbia in 1914 succeed, that almost certainly prevents Italian intervention and leads to an eventual victory
Of the two the River Fleet is the one more likely to be foreseen, as no one could reasonably foresee that the head of Army counterintelligence is a Russian spy, while given Austria's likely enemies the river fleet is the only real way for the navy to influence a war against Serbia
