How to Tie the Water Bowline
If you can tie a Bowline, then tying the Water Bowline is the same with just one extra little step. From what I understand the term Water Bowline came about as this particular Bowline is tied when the rope is wet and slippery. The forming of a second loop when tying the Water Bowline, creates a Clove Hitch, giving the Water Bowline additional security. It is also less likely to shake loose when the loop is unloaded.
ABoK goes on to say: If a Bowline is to be towed through the water a second Half Hitch may be added. Wet knots are apt to jam, and the extra hitch lessens this tendency.