A bottle full of air will give you the same bouyant force as an equal weight of water. A gallon of water weighs 8.3 lbs, so 5 gallons of water weighs 41.5 lbs.

That means that four such bottles will give you 166 lbs of bouyant lift. Enough to lift a light person, but you have to consider the weight of the craft itself. Even if the whole thing only weighs twenty pounds, will you have enough lift for yourself, along with any clothes, gear, and fish you might catch