Put the oil in an oblong bowl. Cut the garlic cloves into small fine cubes. Roughly chop the rosemary and then put everything in the bowl. Also add salt and pepper to the bowl. Add a good dash of lemon juice.
Wash the prawns and stick them on skewers. Mix everything in the bowl and put the skewers in it, the shrimp should be well covered with the marinade. Cover the bowl and let it steep.