Heat the oil in a large skillet set over medium-high heat. Add the prawns and snap peas and cook until the prawns turn a light pink, and the snap peas a bright green, about 2 minutes. Add the stock and marinara sauce, Bring to a simmer, and simmer 2 to 3 minutes, or until the prawns are just cooked through. Serve over pasta or rice.
Note: Marinara sauce is available in the canned and bottled pasta sauce aisle.