You can avoid having to run 12 feet of the tubing by running the stock vent tube straight up and into another larger tube mounted pointing down. The vent tube has to be able to slide easily into the larger tube for air to get in. Make sure the top of the larger tube is sealed.
Now the vent tube is protected from drawing in water by the larger tube covering it, unless you are on your side in about 3' of muck.
Am I making myself clear as mud?