Some descriptions can become a little confusing. With one dry bag to the next, you may see the terms waterproof, splashproof and submersible be passed around. Yes, there is a difference between the three and, quite frankly, the difference is very substantial. When you see a dry bag that is submersible, it means that if you literally submerge the bag in the water your contents will remain safe inside. Now, you may see some manufacturers state their bag is suitable for quick submersion, which basically means for a few seconds and not very deep.
As far as waterproof, these bags will not be affected by water until they are completely submerged in water (unless otherwise stated by the seller). Then, there is splashproof (which you may see some exterior pockets described as). As it sounds, this will withstand light rain and splashes. However, anything more substantial than that and the material can’t be promised to protect its contents.