Tech diving SMBs or dSMBs are reliable surface marker buoys, often known as blobs, to contact the surface to alert others of your location and condition. Attach one to your reel under water, inflate it and send it to the surface to let your boat know where you are or send a message up to them. Sealed or closed cell dSMBs are inflated orally or with a low pressure inflator hose and will stay inflated on the surface even if it falls over until you deflate it. They come in a range of colours and sizes from smaller compact SMBs for travelling to large 3m long buoys to be seen in strong swells. Lift bags are very similar to dSMBs but with greater volume and attachment points to lift items from the bottom and send them to the surface. Look for dump valves that you can use to adjust buoyancy as you ascend and lift capacity based on the item you need to lift.