The key to perfect Ceviche is the freshness of the seafood. The acidity of the lime juice denatures the proteins in the meat, causing it to become opaque, similar to heat cooking. This is known as 'cooking' with acid.
When using conch, which is very tough, it must not only be cut into small pieces but also 'tenderized' (pounded) and marinated longer, for at least 2 hours.
Thoroughly clean the seafood (shrimp, conch, fish) and cut it into small pieces (about 1 cm). If using conch, tenderize it by pounding (e.g., with a meat tenderizer) before chopping.
Place the diced seafood in a large glass or ceramic bowl and pour enough fresh lime juice over it to fully submerge the seafood.
Cover the bowl and place it in the refrigerator. The marinating time depends on the seafood: Shrimp and delicate white fish need 15-30 minutes. Tougher conch needs 2 hours or more.
The seafood is 'cooked' when it changes color from translucent to opaque (white or pink).
Meanwhile, finely dice the red onion, celery, tomatoes, and habanero into uniform small pieces (smaller than 0.5 cm). Wear gloves if handling fresh Habanero.
Once the seafood is 'cooked', add the diced vegetables and chopped cilantro to the bowl.
Mix thoroughly. Taste and add salt and black pepper as needed. For an extra kick, add a teaspoon of Marie Sharp's sauce.
Serve the Ceviche immediately, chilled, with a bowl of corn tortilla chips or fried plantain chips.