Interesting theories.   The Danger Waters lyrics in the DT, which are pretty much as I've found them all over the internet, would seem to clear the waters (no pun intended) a little bit.

Apparently, it's "Danger waters comin'," not "Danger water's comin'." It's "Make me mama no [i.e., not] know," not "Make me [a] mama -- no, no!"
Does our heroine not want her mama to know a) she's having sex, b) she's having sex for money, c) she's pregnant, or d) she's having an abortion?   Is she hollering "Have mercy!" at being 'given' three pregnancies? Sex three times in short succession? Has she been hit three times by her man (client)?

Are "danger waters" the amniotic fluid? I.e., is she about to give birth again?

As to Dave B's story/theory about the croc-filled "danger waters," that doesn't seem to fit the rest of the lyrics.   Would a woman tied to a post in a tidal basin be saying "Hold me tight, baby?" (I'd think she'd be asking her guy to "cut me loose.")

(I must say, though, that this African version of "trial by ordeal," if it was really used, is a bit more sportsmanlike than the European and American versions wherein if the accused woman DIED (e.g., drowned), that proved her innocence (fat lot of good it did her, of course), but if she SURVIVED, that proved she was in league with the devil, so, of course, she would be executed.)

And what is a tortoise boy, anyway?