Extremely simple and good.  You need corn tortillas, some kind of meaty fish, some kind of salsa.  I like guacamole.  I wouldn’t use anything more than this.  Store bought corn tortillas are dry but you can steam them and then keep them in a damp kitchen towel and they will work great.  Or you can try making your own.  It takes some practice, but it pays off.

Mahi Mahi works great.  Just squeeze some lime on it, then coat with light oil and let it marinate for about 15 minutes.  (Much longer and the acid in the lime will make the fish too flaky and the next step won’t work.)  Cut into small pieces and grill.  Get yourself a cast-iron grill pan and you can do this indoors.

Put it all together and eat.  With store-bought tortillas the whole preparation takes no more than 1/2 hour.