So, if I am to understand this correctly; I cannot embark any army based unit (or a scout) to cross an ocean tile until I get the 3 masted tech which is in the medieval era? Quite a few times now my game starts going really well and I take out the other civ on my continent and then I grind to a halt because I can't cross any ocean tiles to plop down new claims for territory. 

Feel like I'm wasting 50+ turns just clicking through since I can't invade anyone else and I can't settle anywhere else. 

Trade expeditions research from the classical era allows your land units to embark, though with only 2 movement points per turn. You are welcome.

Yes, it does, but you cannot cross ocean tiles if they are more than 4 away. Quite a few maps now (maybe spawn related) keep me from exploring anything other than the continent where I first showed up. 

Trade expeditions allows you to embark, but not really travel around much.

Trade expeditions tech to embark units (and you need a sea port, logic)

but if you want to explore then make naval units! they can explore much more and don't take damage from deep sea!

Actually you don't need a port to embark it just remove the mouvement point cost to embark. And a little tip for OP ; the unique unit of the Norsemen is the Langskip wich allow you to embark unit on the ocean but in medieval (three masted is in early modern). Or if you have a science civ (Umayyad is the only science civ in medieval) you can research tech of the next era. So I believe these are the two civ that let you go in the new world in med era.

The Lighthouse of Alexandria gives all your units +2 Naval movement in the Classical era. This should allow you to reach some islands or even a continent if the map layout is favorable. Then you can pick the Norse in the Medieval Era for additional movement and a very good naval ship.

The Three-masted ship is in the Early Modern Era, so getting that Lighthouse can give you a good two Eras headway over the rest to reach the new world. :)