Open the cans of tuna and drain them thoroughly. Press the tuna against the inside of a fine-mesh strainer or press it between two paper towels to get as much water out as possible. Excess moisture is the main reason cucumber boats turn soggy, so take an extra minute here.

Place the drained tuna in a small mixing bowl and break up any large chunks with a fork. Add the mayonnaise, diced celery, lemon juice, salt, and pepper. Stir everything together until the mixture is evenly combined. Taste it and add a little more salt or lemon if it needs brightness.

Rinse the mini cucumbers and pat them dry. Slice each one in half lengthwise so you have two long halves. Use a small spoon or melon baller to scoop out the seeds and a little of the flesh down the center, making a shallow channel. Do not scoop too deep or the boat will collapse.

Spoon the tuna salad into each cucumber boat, filling the channel generously. Use the back of the spoon to press the filling in lightly so it stays put during packing or transport.

Serve right away or transfer to a flat airtight container lined with a paper towel. Refrigerate until ready to eat. If you are packing these for school, place them in a single layer in the container so they do not stack and tip.