Well I'm sorry to say it but I also feel that your choice to drown a living creature to use as a feeder item is inhumane and not something I hope others on this site choose to do. With so many other options available, I'm appalled you've chosen this method.
As far as comparing your choices to what a snake does naturally, that's just a pointless thing. The snake and their prey are acting on instinct and doing what nature intended them to do. You are making what I consider poor choices with a brain able to understand cause and effect and to make informed and responsible decisions.