Marinade for shrimp

I usually marinade my shrimp with the shell on in oil and lemon juice, with a few cloves of garlic. The oil usually sits at the top and lemon juice at the bottom. Should I use a emulsifier or just let it be?

a little dijon mustard would go a long way in solving that problem. I do a similar marinade adding chopped fresh basil - unusual, but really delicious on the grill.