Turns out Blackfathom Deep is a dungeon...

So I have been playing WOW for a couple weeks now, currently level 30, and it has been going quite well. I have been reading, and it seems to be true, that Hunters can level more easily on their own because they have their pets...always two fighting instead of one.
So when I came to Blackfathom Deep at level 25 and attempted to kill the first crab looking thing - well needless to say I got my !@# handed to me over and over.
So I stayed calm, lol sort of, and made the decision "it's fine I will go attempt other quests and revisit this". Now at level 30 I decided to head back, not wanting to leave anything undone.
I get down there and I start attacking these critters one by one; drinking potions and eating - feeding my pet after every tussle...I completed the first quest, super pumped. Then I head to the second; long story short I got ambushed my two sea witches and died. I found myself having to start the whole thing over instead of going to find my body!
I had to shut the computer off and regroup lol So I decided to look up why this was seemingly so hard. Turns out its a dungeon that you are suppose to have 5 people for....! What?! How am I supposed to know this...what tells you that it is a dungeon and you should have a group? lol Anyways I'm giving it another solid go tonight - group or no group lol its getting done.