1. Heat a saucepan, add the clams, cover, and cook over high heat for 2 to 3 minutes until they open. Remove from shells immediately and set aside in a cool place.
2. Squeeze the juice from the limes. Finely chop the shallot, spring onion, and chili pepper. Chop the cilantro and mint. Slice the cucumber into thin strips using a mandolin and cut the grapes in half.
3. In a salad bowl, combine the lemon juice, olive oil, shallot, spring onion, chili pepper, and herbs. Season with salt and pepper. Add the clams, cucumber, and grapes. Mix gently.
4. Marinate for 10 minutes in the refrigerator before serving very cold.
