Great Admiral and ocean bug or feature?

I was playing Maya (immortal, continents, epic). I was on my 2nd great leader and I had hoped to use an engineer to build Notre Dame. The AI built Notre 2 turns before I researched it.

Two CS wanted a great Admiral so in the absence of anything to build for GE, I picked a GA (Actually my first time ever having one ) Much to my amazement I could enter ocean tiles eventhough I hadn't research compass much less Astronomy.

Is that a bug or feature. I was very handy to able to find the other continent in the early AD years, I probably got more than 10 happiness and lot more money trading with the other continent.

Feature.

But remember that the GAdm is a frail unit -- make sure to end each turn on an ccean tile, where barb galleys and triremes can't get him.

Yeah, they are great for exploration like that :3

To answer your question, I believe it's a feature. You aren't using an exploit as far as I know.

It's a feature, but with limitations:

They can't defend themselves, so if they encounter a barbarian or somebody you're at war with they're toast.
They have pretty short sight and you can't autoexplore, so you'll have to micromanage them, which can be a big distraction when you're trying to focus on other things.
You have to pay their gold maintenance cost per turn.

And obviously you probably won't get one unless you're Mayan or you take a few of the Exploration social policies, because if you got one naturally, chances are you have the tech to go into the ocean. So the question is if you really want to go exploration before you have much of a navy, or if you want to burn a great person on an admiral that early on. It may be worth it if you're playing on a map with a lot of small islands, so that you know where you want to settle later, but it's a little pointless if you're playing on continents or anything with unsettled islands.