Heat 1 tablespoon olive oil in a large pot over medium heat until hot.

Add 1 cup chopped onion and 4 cloves minced garlic. Cook, stirring occasionally, until the onion is translucent, about 3 minutes.

Add 2 medium tomatoes (peeled, seeded, and chopped) and 1 medium jalapeño pepper (seeded and minced). Cook, stirring, until the tomatoes soften, about 3 minutes.

Add 2 medium potatoes (peeled and cut into 1-inch cubes) and 1 cup diced carrots. Pour in 5 cups low-sodium chicken broth. Add 1 bay leaf, 3/4 teaspoon dried oregano, and salt and pepper to taste. Increase heat and bring the mixture to a boil.

Once boiling, reduce heat to maintain a gentle simmer. Partially cover the pot and simmer until the potatoes and carrots are tender when pierced with a fork, about 20–30 minutes.

Gently add 12 ounces white fish chunks and 8 ounces shrimp (peeled and deveined) to the pot. Simmer, uncovered, until the fish flakes easily with a fork and the shrimp are opaque and firm, about 5–10 minutes.

Remove and discard the bay leaf. Stir in 2 tablespoons lime juice and 1/4 cup chopped fresh cilantro. Taste and adjust salt and pepper as needed.

Serve the soup hot, garnished with additional chopped cilantro if desired.