Kinda depends on just how "buried" you're gonna go. For normal outdoor use, the Ubiquiti toughcable has shielding (for lighting protection) and UV resistant coating and is quite affordable - if you're looking to lay it under some bark like you would landscape lighting wire, then it'd be fine.. if you're expecting full submersion, then I'd look for something truly rated for burial. I personally don't like working with the stuff because it can be kinda nasty - and if you're doing any kind of substantial vertical run, you absolutely don't want anything gel filled because over time it'll push through the wire and flood your cabinet (gross, and people usually learn the hard way when working on towers).
The toughcable comes in two varieties - Level 1/Pro is shielded and UV Rated; Level 2/Carrier has the braided metal shielding like Coax for additional protection as well as a plastic divide between the twisted pairs like some Cat6 wires. I use a ton of this stuff and have 5 1,000' boxes sitting in my garage... it works well - I have it on a tower, all over many exterior buildings, in 1000' of conduit, and even doing a 75' aerial run between two buildings - and it's never failed me.
If I were worried about heavy submersion like sitting in buried conduit filled with water, then I'd go direct burial gel filled - belden or similar...