Even with the supposed theme/round time fitted into the map, there are still a large number of problems that can easily be spotted, and probably will ruin the gameplay to a small degree, though some may or may not be major in my opinion.
1) The Map Size: Now, when I look at a 64x64x64 sized map, I know they aren't really that large, since they aren't, though they provide a very balanced gameplay experience for a normal amount of players. However, obviously the majority, or really, mainly all 64x64x64 sized maps tend to have a fairly decent amount of height and depth to the map due to the inclusion of a large number of structures.
However... Unlike those maps, there really isn't anything to this map besides a small underwater section.
It's flat.
Keeping it flat, even with an underwater section, leads to boring gameplay, and really doesn't provide much in terms of escape nor chase.
Plus, water-physics are normally terrible in any situation unless merely used as water-vators, as they infinitely slow down any players, basically restricting any means of escape from Zombies for Humans, and can possibly screw over Zombies in chase, as they can't gain any ground on the human and tactically flank them.
The idea being flat moves into my next point...
2) The Aesthetics: Now, I know every map cannot be a masterpiece; and they really shouldn't, as many times it can ruin gameplay. However, this map has nothing in it. It's not very pleasing to the eye. When I was thinking of a map called "Pond_Scum," I was thinking of a large, basin of water with trees towering over the pool on small ridges that players may/may not be able to get up upon, or possibly a large basin in a sunken temple setting (Imagine the "Pit" section of the Sunken Temple from WoW: (
http://farm5.staticflickr.com/4125/5021617308_fa3be43817_m.jpg).
The added terrain adds a heightened gameplay element.
In fact, since that isn't what the map is about, just don't let players into or onto said terrain: Just op'block, adminium, or op'air the areas and keep the map the same. It would retain the same gameplay, just in a better environment.
The map, as it is, does not FEEL like a map I would be interested on playing on.
3) The Gameplay: Now, when I look at a map like this, it makes me think of an Arena-setting map; something similar to Reyvn's Map Glad0s just without the hiding and large-element to it (so just the area around Glad0s herself).
I don't think Arena typed map's are really fit for Zombies. It seems more fitted for TNT, and with added terrain, pathways, tunnels, and the like, very much reminds me of a good idea for an AoD map, as you can actually battle in these areas in tightly-knit fights, which seems pretty cool.
As it stands, again, it does not feel interesting.
This map also reminds me of the map Tower.
Now, tower is much smaller in comparison, though with a similar time-limit.
Tower, in my opinion, just by pictures and gameplay itself, feels more balanced and is just as easy to survive on any other map. This is due to the inclusion of objects, and added height to the map.
I would say, to sum everything up...
It just doesn't feel interesting, and many maps tend to not get picked by players by such ideas.
It also has, from pictures and it's description, flatter gameplay then you will see on other maps.
Just my thoughts.
