In the Clone Wars episode "Cat and Mouse" we are introduced to a thrilling new character: Admiral Trench. Unfortunately, not unlike Darth Maul, he dies before the character does much. But also like Darth Maul, he returns later: in season six of the series. It is obvious to the viewers that Admiral Trench had died when the bridge of his flagship was destroyed by tracking torpedos.
Main (Disney) canon
We don't know. From the fact that he turns up in a subsequent episode with very substantial injuries it can be surmised that he received these during his unlikely escape but aside from that, there's no other explanation offered as to how it happened. It's certainly not the first time we've seen a flag officer survive their ship exploding in a handy escape pod though.
The Star Wars: Essential Guide to Warfare doesn't specifically confirm how Trench survived a point blank volley of his own missiles, but it does talk about his prior escape from the destruction of his earlier ship. Evidently, his armour and physiology make him well-nigh unkillable.
The Republic believed Trench was dead, but he managed to survive thanks to a pressure suit of Andoan mineral-fish armor and his own tough Harch hide. More than a decade later he reappeared, commanding the Separatist blockade of Christophsis from the Invincible.