In a large saucepan, heat oil over medium heat. Add capsicum and onion then cook, stirring, for 5 minutes.
Stir in tequila, water, lime juice, pepper and chillies. Bring to a boil then dump in the mussels. Sprinkle the coriander over the mussels and cover saucepan with a tight fitting lid. Allow to steam for 3 to 4 minutes or until all mussels have opened (discard any that don't).