Peel the cucumbers completely - the skin can turn bitter when blended. Cut in half lengthwise and scoop out the seedy centers with a spoon. Roughly chop into 1-inch chunks. You want about 4 cups of cucumber flesh.

In a blender, combine the chopped cucumber, avocado flesh, Greek yogurt, lime juice, minced garlic, olive oil, cold water, salt, and pepper. Blend on high until completely smooth, about 1 minute, stopping to scrape down the sides once. The soup should be pourable but still creamy - add more cold water 2 tablespoons at a time if it is too thick.

For an extra-silky texture, pass the soup through a fine-mesh strainer into a large bowl, pressing with the back of a ladle. This step removes any fibrous bits but is not required if you do not mind a slightly rustic texture.

Taste and adjust - you may want more lime for brightness or more salt to wake up the flavors. Cover and refrigerate for at least 1 hour, or up to 4 hours. The soup will thicken as it chills; thin with a splash of water before serving if needed.

Ladle into chilled bowls. Drizzle with olive oil, scatter fresh dill over the top, and add microgreens if using. Serve immediately while ice-cold.