Cut tuna into cubes. Alternate 2 shrimp and tuna cubes on a skewer. Brush with BBQ sauce and grill on both sides for about 2 minutes, the fish should still be pink in the middle.
For the dressing, mix all ingredients together well, season with salt and pepper.
Wash the romaine lettuce hearts and remove the stalk so that the leaves fall apart. Peel the cucumber and cut lengthwise into thin strips with a peeler, cut the tomatoes in half. Mix the vegetables with the dressing.
Arrange the salad on plates and place the skewers on top. Garnish with fresh parsley.