The ocean over the continental shelf is quite shallow, relatively speaking. The Pentagon did say that it was shallower than expected where the balloon came down.
The Pentagon also stated that 2 or 3 other balloons were observed during the Trump administration. Trump did nothing, of course, but there is now a fuss being made by Perjury Taylor Greene (among others) about why the military didn't inform the administration that the balloons existed.
If I were in the Joint Chiefs, I wouldn't want to involve the clown circus either.