The most common type of shark in the world's oceans is the oceanic whitetip shark (Carcharhinus longimanus). This species of shark is found in warm and tropical waters around the globe and is known for its distinct long, white-tipped dorsal and pectoral fins. Oceanic whitetip sharks have a slender body shape and are known for their bold and opportunistic feeding behavior.
However, it's important to note that the term "common" can vary depending on the context. There are numerous shark species found in different regions and habitats, and their abundance can vary based on factors such as location, ecosystem, and population dynamics. Other commonly encountered shark species include the great white shark, tiger shark, bull shark, and various species of reef sharks.