Question about Sea To Summit Big River

The bag is basically waterproof - as long as you roll the closure cleanly and as intended 3 times. However, if you submerge the bag and push it under water or load it incorrectly for river swimming so that the closure is always under water, then Seabag is really 100% watertight. Also always a mistake with moisture in the bag is condensation, which forms when warm air is in the bag, which then lies in cooler water for a longer time. But this is not a problem of tightness but simple physics.