Let's talk fish. It can be frozen. Rather than focus on so-called freshness, it's more important to understand how the fish was handled. Was it caught, handled gingerly, and buried straight as an arrow in crushed ice? Then you might want to buy that fish fresh. If it was caught, filleted, and blast-frozen on the ship, then you might want to buy that fish frozen. This recipe gets all restaurant-y, with a playful combination of barely cooked tuna and fresh watermelon. Add more wasabi if you like.