This is the way I did the bow (divider) of my barrel pontoon boat. It cuts much better through water than most other barrel designs i found.
Another advantage is that it is water tight. So it acts as a float unlike most other solutions i have seen which will fill up with water.

To heat up the barrel or drum i used a heat gun. A hair dryer might not get hot enough. It should reach more than 100 degrees Celsius (212 Fahrenheit).

Parts used:
- The bent steel is from a standard 5cm x 5cm (2" x 2") angle steel
- To close the gap i used some poly foam (A stripe from a cheap camping matrass should do as well)
- The filler foam between the bottles is Polyurethane Foam (Not really necessary though)