Sounds plausible to me, provided you've exhausted all possible alternate spellings of the name in an attempt to determine whether "Dessloch" might be a misspelling of another name.
But the element "loch" in a name *is* often taken to mean "lake", just as you stated. "Des" before a name, however, can mean "from the" if the name is of French origin. As in the name "Deschamps", meaning "from the fields".
Interesting name, and logical meaning you've worked out for it, Silver. :)