The use of SMBs on open water dives is almost compulsory, certainly in the UK. They make it easy for the boat to monitor our position, and track us through our ascent. There are a range of options for the SMBs, both in terms of size and method of inflation.
Sizes range from 1m through to 1.8m. The small 1m bag is small and neat and packs to a tiny volume. Its use is only recommended in the calmest of seas, as a significant swell would make it very difficult to spot. The 1.3m or the 1.8m SMBs are preferred in larger seas.
There are three types of inflation method for the SMBs. Manual, low pressure connector, and oral inflate.The manual SMBs are inflated either by using a second stage or the divers exhaust bubbles. They are open circuit, and can spill gas at the surface if a little tension is not applied to the line. The clip on the bag is usually sufficient to close the baffle, though. These are available in 1.3m or 1.8m sizes.
The low pressure inflate SMBs are inflated by connecting a drysuit inflator to a non-locking connector on the SMB, and simply pressing the hose to inflate the bag. These are much easier to use than they sound! They are closed circuit, so will not spill gas on the surface. An overpressure valve prevents the bag from being over-inflated. These are available in 1, 1.3 and 1.8m sizes.
The oral inflate SMBs have a small valve attached which allow the bag to be inflated by blowing into the tube. They are very simple and easy to use. However, they do not incorporate an overpressure valve, so great care should be exercised if inflating them from depth not to ut too much gas into them. These are only available in the 1m size.
Don’t forget that for an extra Â£10 you can get a Divesigns SOLAS name label fitted to your DSMB. Well worth it!