A SMB or Surface Marker Buoy is absolutely essential kit for diving any where that may have surface traffic. An SMB allows your position to be known by people watching from shore and watercraft, whether they be the boat you are diving from or other water users. SMBs such as the Seac Sub Torpedo are inflated before you get in the water and stay up during the whole dive, whereas the AP Valves SMB is designed to be deployed from depth at the end of or at any critical point during a dive.