Ceviche

... was originally a Peruvian dish, even if according to Wikipedia it's now "popular in the Pacific coastal regions of western Latin America." In Peru, "ceviche has been declared to be part of the country's national heritage and has even had a holiday declared in its hono[u]r."

Wikipedia covers Mexico in the same section as the USA and Central America, where "it is served either in cocktail cups with tostadas, or as a tostada topping and taco filling. In Mexico, when served in a cup with tomato sauce, it is called a ceviche cocktail. Shrimp, octopus, squid, tuna, and mackerel are also popular bases for Mexican ceviche."

Especially pertinent to the question is the description of the marinade. In South America (according to Wikipedia) it's "freshly squeezed key lime, with sliced onions, chili peppers, salt and pepper"; but in Mexico, USA and Central America, "The marinade ingredients include salt, lime, onion, chili peppers, avocado, and cilantro (coriander). Cut olives and tomatoes are often added to the preparation (ketchup is not used because it adds sugar and is not fresh)."

So either way, lime juice would seem to be the only liquid ingredient.

And just in case anyone else is wondering what a tostada is, it's any dish that includes a toasted tortilla as its main base.