Whether you're an avid tech diver or just started diving, a Surface Marker Buoy (SMB) is an essential part of every diver's kit. Divers use surface marker buoys to make others aware of their location in the water, adding an extra safety layer when there can be other divers, swimmers or boat traffic in the diving area.
SMBs can also be used to relay messages to the surface. Colour coding is very important here, as a yellow SMB stands for underwater issues or emergencies, while all other colours (mainly orange or pink) simply show there is a diver underneath the surface.
SMBs range in size and volume and there are different models, some of which are for surface use and some of which can be deployed underwater as well (the so called Delayed Surface Marker Buoys or DSMBs).
For technical divers an SMB can be easy way to do their deco stops while hanging at a fixed depth as well.