I'd just note that I've had a number of aquariums that are put together with silicone. They are most definitely underwater, quite thoroughly stuck together, and, in the case of salt water reef tanks with HID lighting, subjected to substantial UV. No failures yet. Needless to say there's silicone and there's silicone. Dow makes probably 200 different products for different applications, some of the mil spec RTV silicone adhesives are amazing in what they can do, especially where a flexible seal is required.
Yes, I have also seen disasters created with indiscriminate use of caulks and glues of all kinds! As a player piano rebuilder I can't really tell you whether I hate silicone or Elmers glue more.
As a sealer applied in the appropriate places in the appropriate amounts it can be fine, I certainly don't mean to suggest that it's a substitute for a proper repair.