Frank,
I think some people are missing the point from your orginal post.
Correct me if your wrong.
Not knowing where you operate I assume you are saying that your governing body uses regs that mimic part 135 regulations, not that you are require to have and operate under a FAA part 135 certificate. To hold a a FAA air operating certificate you must be a US company owned by a US citizen.
As far as Part 135 regs go, to fly off shore all that is relevant is VFR wx min, Requiremts for floats ( extended overwater operations) , PFD/ Rafts, . I dont have a FAR with me so I cant quote it directly.
What really becomes more important and relevant is what is in your Operations Manuel. That enables you or limits operations. ( offshore mins, flight following, sar , night, med-evac, fuel min's, deck landings training requirements etc.) Ops manuels for part 135 are operator specific and approved by your POI (operations inspector for the FAA).
hope that helps
RB