Prepare all ingredients as listed.
Combine the sliced cucumber and water. Refrigerate while preparing the meal.
Place the potatoes in a saucepan and cover with cold water. Add salt. Bring to a boil, then simmer for 12–15 minutes, until tender but still holding their shape. Drain well.
While the potatoes cook, combine the sliced red onion, red wine vinegar, and dried oregano. Let stand for about 10 minutes.
Add the warm potatoes to the onion mixture. Fold in the cherry tomatoes, olives, capers, and fresh basil. Season with black pepper and drizzle with extra-virgin olive oil. Toss gently and set aside.
Heat the grill on medium-high heat.
Rub the salmon with the olive oil, then season with black pepper and lemon.
Grill the corn on all sides until tender and lightly charred. Brush with olive oil and season with black pepper.
Grill the salmon on both sides to an internal temperature of 145°F (63°C). Spread with pesto sauce.
Serve the salmon with Sicilian potato salad, grilled corn, watermelon, dates, and cucumber water with ice, if desired.