I tried to get an "everything" bike by getting a hybrid. I sold mine after 6 months of usage. For me personally, the hybrid was not good on trails nor good on road. The hybrid was slipping on the trails and too heavy for the road.

I would get a used mountain bike for trails and a used road/touring bike from Craigslist for the road if $700 is your price range. Also, tax-free on Craigslist compared to prices in stores. I could not imagine using a hybrid for a sprint triathlon. It would take me forever to finish, even if only for 10 miles.