What a waterproof rating actually promises, and for how long

What follows is an argument about water resistance ratings, and about where the received version of it stops being true.

Two digits, two different tests

An ingress protection code has a first digit for solid objects and dust and a second for water, each defined by a specific laboratory procedure. A six in the first position means dust-tight after a defined period under partial vacuum, which is a stricter test than most people assume.

Levels in the second digit are not a simple ladder: spray tests and immersion tests examine different things, so a device rated for immersion has not necessarily passed a high-pressure jet test. Manufacturers therefore sometimes quote two ratings, which is a sign of care rather than confusion.

The immersion test is very specific

The common immersion levels specify fresh water, a stated depth, a stated duration and a device that is stationary. Movement through water raises pressure well above the static value, so swimming with a device exceeds the tested condition even at trivial depth. Water temperature is also specified, and thermal shock from a cold device entering warm water can draw moisture past seals.

Mechanically, none of this makes the rating dishonest; it makes it narrow.

What is definitely not covered

Salt water corrodes contacts and leaves deposits that hold moisture against seals, and no consumer rating includes it. Soaps and detergents lower surface tension, which lets water pass gaps that would otherwise hold it out, so a shower is harsher than a pool. Steam is fine enough to enter through pressure equalisation vents that liquid water cannot pass.

Under load, chlorinated and mineral-rich water leave residues on adhesive seams over repeated exposure.

The rating describes a new device

Waterproofing depends on adhesives, gaskets and mesh that age, harden and shift under heat and impact. A drop that produces no visible damage can break a seal, and there is no way for a user to see that it has happened. Manufacturers state clearly in documentation that resistance is not permanent and is generally not covered by warranty, which is the sentence nobody reads.

After a repair, resistance depends entirely on whether the seals and adhesives were correctly replaced.

What to do when a device gets wet

Power it off, dry the exterior, and leave it in a dry airy place rather than powering it up to check. Rice is ineffective and introduces dust and starch into ports, which is a well-documented piece of folklore rather than a repair.

Rinsing in clean fresh water is the correct first step after salt water, which is counterintuitive and matters. Charging a wet port is the most common cause of corrosion damage, and phones that refuse to charge while damp are protecting themselves.

Firmware updates change this behaviour more often than hardware does.

Reading the marketing

Water resistant and waterproof are marketing words with no fixed definition; the numeric rating is the checkable claim. A depth in metres printed alone usually comes from a different standard designed for diving watches, which tests pressure rather than immersion time.

Any device sold for swimming should state a specific standard and the activity it covers. Assume the rating decays and treat it as protection against accidents rather than as permission.

The takeaway

The number covers clean still fresh water on a new device. Everything else is your risk.

The constraint is almost always physical, and marketing rarely mentions which one.