The verb drown means to die from inhaling water into the lungs and being unable to breathe. It is possible to drown in even a small amount of water, so it's important to learn proper water safety.
You can also use this verb with a direct object: for example, a flash flood might drown animals that live near a river. You can drown things in a less literal way as well. If you drink alcoholic beverages to forget your troubles, for example, you can say you're trying to "drown your sorrows." If you're submerged in a tidal wave of school assignments, then you are "drowning in work."