Put a medium saucepan filled with water on medium-high heat and add the shrimp to partially cook it; if the shrimp is frozen this is an easy way to defrost it.
While that is cooking, heat the oil in a large pan.
Once the water reaches a boil, drain the shrimp.
When the oil in the frying pan is hot, put the shrimp in to finish cooking, 1 minute.
Next, stir in the pineapple and let that cook for 1 minute
After that, add the rosemary, mix it all together and let the shrimp soak up the pineapple juice.
Finally, take the pan off the heat and let it cool down a little bit.
Serve right away!
Optional: Plate it on top of rice. Enjoy! :)