I think the main channel of the BAM is closer to 300 meters than 300 feet. It's been a few years since I went through it.
I checked and you are correct; I was conflating meters and feet, 310m to be precise.
Yet it was easy enough to cross in numbers during the late Pleistocene that people from the southern Arabian Peninsula and the Horn of Africa were ethnically the same people, as projectile points and other artifacts have recently confirmed. Hence the description in Genesis 2:13 that the second river 'Gihon encompassed the whole Kingdom of Ethiopia' was factually correct (recent archaeology and hunter-gatherer ethnography have both suggested "Eden" was then under what is now the Persian Gulf). Sea levels have risen about 120m since then.