What IPX7 actually promises

IPX7 means the device survived being submerged in one metre of still, fresh water for thirty minutes, in a laboratory, as a new sample. That is a specific and fairly demanding test. It is also narrower than most people assume. It says nothing about hot water, soap, chlorinated pools, salt water, or what happens to the seal after two years of being pulled open with wet hands.

Where the rating stops applying

Soap is the part that catches people out. It lowers the surface tension of water, which lets it creep past seals that hold fine against plain water. Shampoo and shower gel do the same thing. A toy rated IPX7 can be perfectly fine in a basin of clean water and fail in a bath with bubble bath in it, and neither the box nor the listing will mention that. Heat matters as well. Warm water softens silicone slightly, and a seal that is tight at 20°C can weep at 40°C.

The test conditions nobody reads

Ratings are given for a new unit in still water. They are not given for one with a hairline crack in the flap, or one where the flap has been stretched by being opened twice a day for a year. This is why the same model can be genuinely waterproof when it is new and stop being waterproof long before it stops working. The rating is a statement about the design, not a guarantee about your particular unit eighteen months from now.

What the word "waterproof" is worth

In the UK there is no legal definition of "waterproof" for consumer products and no body that enforces one. A listing can use the word and mean nothing specific by it. IPX ratings come from IEC 60529, which is an actual standard with an actual test behind it, which is why a stated IPX number is worth more than the word ever will be. If a product says "waterproof" and gives no IPX figure at all, treat it as claiming splash resistance at best.

How to judge it before buying

Look at the charging arrangement first, because a rubber flap is the weak point and magnetic contacts remove it entirely. Then look for a stated IPX number rather than the word "waterproof", which has no agreed definition and can mean anything. Then read the one-star reviews and search them for "water" or "stopped working". Seal failures show up there far more often than motor failures, and they show up early.

Testing one you already own

You cannot improve a seal, but you can find out whether yours is still intact before it matters. Dry the toy, close the flap, and hold it under a running tap for thirty seconds. Running water, not submerged. Then dry the outside and open the flap. If there is moisture inside the port, the seal is already gone and the toy is living on borrowed time. Do that test before you take it into a bath, not after.