A delivery device and system to supplement CO2 in an underwater environment without the need for electricity or the use of compressed CO2. The device consists of a container containing a biological organism such as mycelium and including an exit portal for CO2 to enter the underwater environment. The device may also incorporate a separation device to delay and control the flow of CO2. The system requires the device to be held in place through a securing point in the underwater environment. The minimum requirements for the device are described, but in certain instances it will be preferably used with a double-bag or an outer shell housing to protect or aesthetically conceal the placement underwater. The use of this device and system to supplement carbon dioxide in water will span many industries and applications. It will assist with mosquito trapping. It will also supplement CO2 in underwater growing environments.
