On visits to Baja California, I've had Cóctel del Mariscos: fresh seafood (shrimp, fish, clams, scallops, octopus, whatever) with chopped celery, scallions, serranos, tomatoes, etc. marinated in lime juice and salsa, served with tortilla chips. Several places had a mild version for turistas and a picante mix for locals, which I preferred. A trick I picked up was to shell the shrimp and pop them in boiling water for one minute, rather than marinating them for hours in lime juice.
Ceviche is similar, with less juice. Avocado is sometimes added before serving.