Pat the shrimp dry and toss them in a bowl with the blackening seasoning until coated.
Heat olive oil in a skillet over medium-high heat. Cook shrimp for about 2 minutes per side until blackened and cooked through.
In another bowl, mash the avocado with lime juice, cilantro, salt, and pepper until smooth but slightly chunky.
Arrange cucumber slices on a platter. Add a small spoonful of avocado mixture on top of each slice.
Place one blackened shrimp on each cucumber-avocado base and serve right away.