Wash cucumbers thoroughly under cold running water. Cut each cucumber in half lengthwise, creating four boat-shaped pieces. Using a spoon or melon baller, carefully scoop out the seeds and some flesh, creating a hollow channel about 1/2 inch deep.

In a medium bowl, combine Greek yogurt and peanut butter until smooth and creamy. The mixture should have a thick consistency that won't run out of the cucumber boats. Add honey if desired for extra sweetness.

Gently fold blueberries and chopped mint into the yogurt mixture. Ensure blueberries are distributed evenly throughout the mixture for consistent flavor in each bite.

Using a spoon, carefully fill each cucumber boat with the yogurt mixture. Don't overfill – the mixture should sit just below the cucumber edges to prevent spillage during freezing. Smooth the surface gently with the back of the spoon.

Place filled cucumber boats on a parchment-lined baking sheet, ensuring they don't touch each other. Freeze for 3-4 hours until completely solid.

Remove from freezer 2-3 minutes before serving to prevent the treats from being too hard on your dog's teeth. Cut larger boats into smaller portions for small dogs.