Buoyancy Arms

Inon float arms or the 2" ULCS buoyancy arms?

or TLC/Aquatica Buyoancy Compensating Floats?

There are also many inexpensive DIY solutions, but most of them will compress the deeper you go.

Stix...

Against the grain, I have to say that I prefer UCLS; smoother, less catchy, more durable and I suspect less water resistance. The downside is they are not adjustable: you need to get buoyancy right when purchasing and maybe sort out a way to trim for lens/port variations.

If you do choose 2" dia UCLS make sure you buy the longer reach ball clamps which allow a pair of arms to fold 180 deg.

I happily used those kids tubular swimming float things for my first couple of years but they do compress and offer less buoyancy at depth. Nevertheless, a good starting point if budget is limited due to buying lots of other kit.

depends on how much buoyancy you require. I use the Inon Float arms as my rig is over a kg without it, and I need at least 600g positive buoyancy. (This will reduce when I add the second arm/strobe, as the second arm I intend to add will have a further float arm, reducing the weight to ~ neutral.)

Stix

I like my stix. Easy to pack, easy to adjust for different ports/lenses.