Floating keychains are compared on size, colour and price. None of the four questions below is about any of those.

How much key weight will it hold?

Net buoyancy is displacement minus everything on the ring, and a car fob is heavy.

Ask for a payload in grams. A supplier who only offers the word floating has not done the sum.

Does the material absorb?

Closed-cell EVA does not. Open-cell foam and unsealed cork do, gradually.

A sealed hollow body does not either — until a puncture makes it a sinker.

Which way up does it sit?

Weight low and volume high makes a fob self-right under load.

A flat symmetrical slab rides edge-on and disappears in chop.

Is it attached to anybody?

Over moving water, a wrist coil or clip is the plan and the float is the backup.

Remember the coil’s own mass comes off the payload.

Then choose the colour

Fluorescent orange or yellow-green for daylight, reflective for a torch.