The problem here is not to expend more energy running around trying to fill up balloons than there is methane energy to catch. Methane clathrates trapped in ocean sediments are in the first stage of a very slow concentration process. When they sink enough and a gas impervious layer forms above them, they start to form the beginnings of a natural gas well. A few million years and some moving of tectonic plates and it may even be economical to drill down to them and put the gas into a pipeline.
A better way would be to use the methane that is thrown away as a bothersome nuisance now. The number one crime against nature is to flare gas instead of compress it and save it for human use.
These two kids watching a gas flare near their home in the Niger delta probably have to go out to collect firewood every day because it is "uneconomical" to collect the gas and distribute it to their house.
And with all the manure and vegetation that rots all around us, new sources of methane are ubiquitous. That hog farm with the sewage lagoon that stinks up half the county? Put a lid on it! All those landscapers headed for the landfill with a load of trimmings? Send them to a biogas plant. There is no need to LOOK for methane, when all that has to be done is to THINK about using what is decomposing all around us.