Can't build Offshore Platforms

[jbcummings]

Has anyone built Offshore Platforms? According to the Civilpedia the required technology is Plastics (not sure why, but OK). Yet even with Plastics researched I find no way to build an Offshore Platform, even though I've had Oil showing up just offshore of one of my cities.
Any suggestions?...or is this a bug?

 

[Zanmato]

Are you using workboats? Send a workboat out to the Oil resource then the option should appear.

 

[jbcummings]

Why didn't I figure that out?

Thanks.