Sub caught in a explosion?

[Von Talon]

I was attacking to Passenger/Cargo -ship with my deck gun. I didn't want to waste a torpedo to it. After lot of shells, the ship started to sink. I was about 50-100m (quite close). "She is going down" -message appeared. After 5 minutes, the ship started to explode. Suddenly, I get alot of damage reports.
My sub was severly damaged: Batteries destroyed, Diesel engines destroyed, bridge destroyed, deck and flak gun destroyed. Almost every part of my sub was destroyed and critical leak in every compartment. And every watch was dead. First, I thought that I was under attack, and I ordered to dive (dumbest decision EVER). Then I realized that I was caught in the explosion. Well, I noticed that my sub couldn't hold periscope depth, and asked from the navigator: Whats the depth under keel? -46 meters, he answered. As you can guess, I sank to the bottom. I ordered everyone to fix the boat. Luckily, I had many repair fellows becouse my sub gets damaged very easily

I managed to pump the water out and fix some critical parts, and then surfaced. Was my sub cought in the explosion of the enemy vessel?
I can't find any other explanation for this.