Pros:

It's huge
Nice idéa
Can't get too many boat maps
Dark

Cons:

VERY rugged design
Repetitive... All rooms are basically 'big square with objects'
No supplies... Only 5 weapons (all that I've found)
Very few zombies, probably due to size
Too easy to avoid tanks

Conclusion:

I can't give this a great score, because it feels like it's not even close to a beta. Very few zombies for some reason, too repetitive rooms, and close to no weapon diversity. I don't care about graphics, but if anyone that does sees this, it'll put them off big time. It's a good springboard for a better, more finished, version though.