Hi Experts! This week's map is the Underdark Basin (35x35), a map with just as much water as land so I hope your players can swim/fly/run really fast/float. As always, whenever I add abnormal terrain I recommend occupying it with enemies who don't find it so troublesome, but you could always throw your players a bone and make the enemies just as mobile as them... now that I think about it how cool would it be if someone in your party can walk on water and so can someone on the enemies' side, they could have a ridiculously dramatic 1v1 on the surface of an underground lake.
Your alternate versions of this map are Caustic and Grimy! I've made these variants enough that they probably don't need explanation- the caustic one has horrible glowing water and is probably downstream from some sort of industrial district while the grimy one is probably runoff from a sewer. They're 2 different versions of water that your party should 100% avoid swimming in, but you know there's something living in there that loves that yucky stuff and wants everyone to get real comfortable under the surface with them.