"Courtney Thomas,,," asked:
Good ? Bad ?

Depending on your intended use, good for shallow diving. I'd recommend
that you get some SCUBA instruction before any kind of diving, even
for a device as "simple" as this.

Personally, in the realm where these things are useful, I'd rather
just snorkel and free dive, rather than mess with this type of device.
If I hafta/wanna support some kind of dive-related machine, I'd just
as soon go ahead and have a compressor to fill tanks.

YMMV,

Frank