Start by chopping the peeled, deveined shrimp into bite-sized pieces and place them in a large mixing bowl.
Squeeze the fresh lime juice over the shrimp, ensuring they are fully submerged. Toss gently to coat evenly and set aside to marinate for about 15-20 minutes until the shrimp firm up and turn opaque.
While the shrimp marinate, thinly slice the red onion and chop the cilantro. Dice the tomato or cucumber, and prepare the chili or hot sauce for heat.
Once the shrimp are opaque and firm, add the sliced onion, chopped cilantro, diced tomato or cucumber, and chili to the bowl. Mix gently to combine all ingredients thoroughly.
Season the ceviche with salt or fish sauce, tasting as you go, to achieve a balanced, flavorful punch. Stir again to evenly distribute the seasoning.
Cover the bowl with plastic wrap and refrigerate for at least 30 minutes to let flavors meld and the seafood to stay chilled.
Remove from the fridge and give it a gentle stir. Taste again and adjust seasoning or citrus if needed.
Serve the shrimp ceviche chilled in small bowls or glasses, garnished with extra cilantro if desired, and enjoy the bright, zesty flavors with a satisfying chewy texture.