A tow float is not a lifebuoy — it doesn't hold you up if you're unconscious. What it does is make you visible and give you something to grab. Those two functions matter more than any other piece of gear you can add to an open water swim. A swimmer at 50 metres from a boat is invisible in anything but flat calm. A bright orange tow float at the same distance is conspicuous. That gap — between invisible and visible — is the one that matters when a kayak, jet ski, or fishing dinghy turns towards you.
Open water is shared with boats, and boats don't expect to see you. Most tow floats are visible from roughly 200 metres in good conditions; in chop, mist, or low sun that drops significantly — which is exactly when you want the float rather than just your swim cap. Colour matters: bright orange and high-visibility yellow test best in all light conditions. Pink and red work in flat calm. Blue and green are all but invisible and should be avoided entirely. If you swim at dawn or dusk, look for a float with reflective strips or a dedicated light attachment point.
The second function is less dramatic but equally real. Cramping is one of the most common reasons swimmers get into difficulty in open water, and it doesn't announce itself. If your calf seizes at 400 metres from shore, your options are swim through it — often not possible — or stop and float. A dry-bag tow float holds roughly 20 litres of air, more than enough buoyancy to rest on while you work the cramp out. You can't lie on it like a pool float, but you can stop swimming without sinking, which buys the time you need to recover or signal for help.
There are two main types. Dry-bag floats (Zone3, Orca, Decathlon, Swim Secure) are an inflatable pouch on a waist strap — you inflate by blowing, and they double as a dry bag for keys and phone. Most come in 20–28 litres; 20L is fine for solo swims, 28L if you want the extra buoyancy or storage. Dedicated buoy floats are firmer, brighter, and easier to rest on, but they carry nothing. Either way: choose the brightest colour available, confirm there are reflective strips for low-light use, and check that the tow line is adjustable — you want it running 1.5 to 2 metres behind you, not tangled at your heels.
Attach the waist belt so the clip sits at the small of your back. A properly fitted tow float adds roughly 3–5% resistance — noticeable in your first session, imperceptible after that. Don't clip it to your wrist; it belongs at the waist so it trails in your swim line, not through your stroke. If you don't already own one, pick any Zone3, Orca, or Decathlon model in orange or yellow for around £20–35. That single purchase is the highest return on safety per pound in open water swimming — buy it before your next solo swim.