Halcyon Big 45 foot surface marker buoy. This bright orange marker can let your buddies and the boat know exactly where you are. Excellent for doing deco in the ocean where the boat needs to know where you are. This is closed circuit oral inflate.
You can inflate this 2 ways. You can blow into it like a straw or use your BCD or drysuit hose. The nipple on the inflator doesn't have a lock so you just need to apply pressure to fill and it stops inflating as soon as you let the pressure off. Very simple.