On Mon, 20 Sep 2004 11:47:34 -0400, Sonco put forth the notion that...
You can't use Romex. Assuming local ordinances aren't requiring anything new to be run underground, you can use minimum #8 single conductors supported with porcelain knobs like a service drop, or use messengerized cable as you mentioned.
You really should follow code regradless of where the installation is. The code is designed to provide a minimum level of safety that people who have many thougsands of years of expereince have deemed appropriate. Sometimes the reasons for things are not obvious but there are generally solid reasons why the code is written as it is.
I would be very suspicious of running 25 feet of UF without support.
BTW Romex is a trade name, but is also commonly used to describe type NM cable, the stuff you see fished through walls. UF cable iks underground feeder cable, and might be made by Romex but is a diffferent cable.
You can't use NM outside at all because it is not suitable for wet locations.