Sure you can understand it - it's quite simple, and only requires two sound changes (though the reality of the vowel fusion was probably a bit more complex).

All of the sounds in -eaux used to be pronounced. (Three vowels pronounced together like this (without hiatus) is called a "triphthong", if you're interested.) But, as we famously know from other words in French, final consonants were lost (under specific circumstances), so -x stopped being pronounced as part of that general change.

Also, -eau underwent fusion. The three vowels sounds coalesced into a single sound that preserved parts of all of the three original vowels. The height of the [e] was preserved as a mid vowel, the backness of [a] and [u] were preserved, and the rounding of [u] was preserved, resulting in [o].

Just like English, however, French orthography wasn't updated to account for this change, and so we can see the history of the language in the differences between the way it's written and the way it's pronounced.