Wow, this level seemed like it's specifically designed to be as annoying and unfair as possible.
Exiled Bowser wrote:I have to warn you guys it is designed to be world 6 difficulty so be on your toes.
There's a difference between difficult-but-fair and this level. Because the Thwomps are sprite-swapped to look
EXACTLY like the normal spikes, it's impossible for the player to differentiate between the two with the exception of an
extremely minor graphical shine when the player stands near a Thwomp sprite-swap. This means that all first-time players will get hit by at least the first Thwomp that's in a narrow corridor and possibly many others unless the player slowly approaches every single downward spike with caution, and that just isn't fun. Remember: above all else, never be inconsistent. In other words, never have the same graphic (or what's basically the same graphic) sprite-swap two different AIs. Plus, even if it weren't for the existence of two different AIs sharing the same graphic, the spikes blend in with the background, so if there's a Thwomp sprite-swap just floating in midair (like the VERY FIRST ONE, which is
before the sign that warns about falling icicles, I might add), first-time players won't notice it until after it has already begun falling down.
Honestly, that would be enough to prevent this level from being Pretty Good, but the level has other problems as well.
For starters, the distance between the spikes in the center of this screenshot is exactly 2 units, meaning Super Mario won't be able to get past without getting hurt:
Next, you have the pipe blocked by ice blocks, but they can't be removed with fireballs.
It would be better if you used the dragon coin-blocks instead, because that would silently tell the player that the only way to access the pipe is to get all the dragon coins.

Also, you forgot to make the ax invisible:
This part is also the best example of how unintuitive the level really is; when the player gets the ax, a message pops up that tells the player to run (due to a spike wall that will chase him/her), but if he/she
does run, he/she will get hit by the first Thwomp sprite-swap on the way due to the low ceiling. Once again, the only way to avoid the Thwomps is to either memorize where they are or go through the level slowly, but if the player goes slowly here, he/she will get hit by the spike wall that's chasing him/her! There's literally no way that first-time players
won't get hurt here unless they already activated God Mode before this part.

By the way, having slippery blocks underwater prevents the player from being able to walk from a standstill; in other words, slippery blocks should never be used underwater. Also, the warp exit doesn't give the player any sense of accomplishment since the level just ends when the warp is entered. It would be better if you replaced the warp with another SMW star.
Lastly, there's all this:
1) by having the warp placed half a unit above the bottom of the pipe, the top of Super Mario's sprite is cut off. 2) Why is this pipe even here? It serves absolutely no purpose.

3) Because the spike wall mentioned earlier doesn't disappear at the end of the chase, it can still catch the player off-guard by floating up here. 4) Why is this part even here? It takes zero effort for the player to swim from the previous screenshot to here, hit the ? switch to deactivate the blocks, and jump over to the pipe that leads to the exit. Honestly, you could remove the entire right-hand screen-and-a-half from this section and make the pipe in the previous screenshot lead to the exit, and nothing of value would be lost (in fact, it would help to streamline the level if you did that).

One more thing: although you had switches that would change the ice to water and vice versa, there's literally no incentive for the player to turn the water back into ice, making the main draw of the level completely pointless and gimmicky.
Summary:
GOOD:
-Graphics aren't terrible.
-Music fits the level well.
-Block placement is okay.
BAD:
--THE THWOMPS HAVE THE EXACT SAME GRAPHIC AS NORMAL SPIKES AND BLEND IN WITH THE REST OF THE LEVEL TOO MUCH.
-One of the dragon coins is impossible to get as Super Mario.
-Unintuitive secret star (un-melt-able ice blocks).
-The ax isn't invisible.
-Seriously, never make enemies look exactly like normal blocks (or spikes, in this case).
-Don't use warp-exits in stand-alone levels; they end the level too abruptly.
-The entire right-hand screen-and-a-half from Section 5.
--THE MAIN MECHANIC IN THE LEVEL IS COMPLETELY POINTLESS SINCE THE PLAYER NEVER HAS TO CHANGE THE WATER BACK INTO ICE.
In conclusion:
This has the potential to be Pretty Good, but all it does is lure the player in with the promise of water/ice puzzles only to kill the player countless times with falling icicles that have the exact same graphic as normal spikes, among other flaws. Because of that, I'd say this deserves a 2.5/10