04 key and remote

I was in my boat when my brother dropped my boat off at the boat ramp in the durango. He parked it and went to the dock to get in. Well in his wisdom, he throws the keys to me instead of handing them to me when he got in. Well, he missed my hand by, um about 5 feet. So, now they are 20 feet down on the bottom of the lake. So, what is the cheapest way to get a new key for it? I really don't want to pay $100+ dollars from the dealer. Any advice would be great.