In a large glass, mix oil, garlic, thyme, salt, pepper and marjoram.
Add salmon, bell pepper, and shrimp and mix to coat well.
Cover the dish with plastic wrap and let marinate 15 to 30 minutes in the fridge.
On 8 metal or wooden skewers previously soaked in water, thread salmon cubes alternating with the bell pepper and shrimp.
Heat grill on medium heat.
Put seafood skewers on oiled and close the cover.
Cook 6 to 8 minutes or until salmon flakes easily with a fork (flip the skewers at mid-cooking and baste with marinade).
Serve the skewers with lemon or lime slices and dip in Tzatziki, if desired!