That's exactly what I thought too! If you're crawling through water, there's no way water won't get in through the top, and maybe even the tongues of the boots. So by that thought, it seems to me that it's far more important for them to be quick dry than anything else, unless you're ok with wearing the issued bricks while waiting for yours to dry.
We went to USAFA BX to look for boots figuring they should have their own regs, or something that's in regs, right? Nope. They had some Belleville ultralights, and the Rocky C050s. That's it. (They had 2 other models that were steel toed.) My appointee tried on several options, including the Oakleys (ordered from Amazon using their try for 7 days free option) and Rocky C050 and C072. Oakleys were very lightweight comfy and dries fast, but zero support. Heels flopped around, and nothing in terms of ankle support. They dry super fast though. The Rocky were far more cushiony, offer more foot, heel, and ankle support. They are heavy (will definitely need breaking in, and adjusting to) and because they are supportive, they're thicker, and won't dry quickly. I've come to realize there's no such thing as the perfect boot. Get what you need to get you through BCT, and worry about other boots later when regs are more relaxed after BCT.
One thing I really like about Rocky boots over other brands is the soles are stitched on. I've seen some Amazon reviews about the Bellevilles and Oakleys' soles busting apart, and not making it through BCTs, so that may be something to consider.