a parachute style flaregun, that launces, then covers, oil miner in ocean,
to cut off the air supply
first thought was 'the dome' like in movie of aforementioned name, also in simpons movie
source
https://upload.wikimedia.org/wikipedia/commons/thumb/6/6e/British_airborne_forces_training_alongside_NATO_counterparts_MOD_45160115.jpg/250px-British_airborne_forces_training_alongside_NATO_counterparts_MOD_45160115.jpg