Place the crawfish, crab, and shrimp in a large glass or ceramic bowl; pick any shells from the meat. Pour in the lime juice, and gently mix, being careful not to break up the crab meat. Cover and refrigerate for 1 hour.

In a separate bowl, mix together the ketchup, hot sauce, and olive oil. Stir in the cilantro, onion, cucumber, jicama, and jalapeno; add salt to taste. Gently fold this mixture into the seafood. Refrigerate until ready to serve. Add the avocado just before serving.