The 88mm Flak guns had a fearsome reputation and it was well deserved. The were designed as anti aircraft guns, but were great anti tank guns as welll and were used as artillery on occasion. The Allies had nothing ike it. While the Germans had a large number of different caliber weapons from domestic production and captured stocks, the characterization that everything shooting at you was an 88 is pretty accurate. If it is shooting at you, it seems like your worst nightmare! (an 88!). The same thing happened to tanks. Almost any tank the Allies encountered were Tiger tanks even though they were relatively rare. To be fair, the Mark IV had vertical armor like the Tiger, so I can understand how in the heat of combat mistakes can be made. Mistaking a Panther for a Tiger requires a lot more imagination.
While the German Navy used the 88 to defend shore stations, they did not as a rule use the same weapon as the Army (Flak 18 or 36/37). They had some navalized 88mm guns that could not shoot the same ammo and the Flak guns or Tigers. They also had some old WWI guns that were used in secondary roles.