Try LifeProof.

Dexport said..
As far as I know the iPhone 7 is waterproof. I have the 7+ and it is but only down a few meters. Handy if its in your pocket and gets splashed though.

Hi Dexport,
thanks for the feedback - some research turned up the following:
From:
everymac.com/systems/apple/iphone/iphone-faq/differences-between-iphone-7-iphone-7-plus-models.html (excellent site for iPad/iPhone/iPod/ etc info)

"Both the iPhone 7 and iPhone 7 Plus models use all aluminum cases with softly rounded sides and are splash, water, and dust-resistant (IP67), but they are not water-proof"

Some iPhone cases claimed to be waterproof are specified as 30mtr/100ft, but they all seem to use the same sealing system which look like it would be compromised by a single grain of sand in the wrong place.
Some reviews of these types reported failure of the seal and flooding, so I'm a bit wary.
regards,
allan

On the apple website for the iPhone 7 they say:

Rated IP67 (maximum depth of 1 metre for up to 30 minutes) under IEC standard 60529

I have had my iPhone 7 for over 18 months and have used it numerous times underwater for video and photos tho never deeper than half a metre. I have washed it countless times to get salt off after sailing and have had no water ingress whatsoever. (Maybe just lucky).
On other phones (iphone4) I used the life proof case which kept the phone in pristine condition - totally unmarked in 5 years of heavy use.

Allan,
I've got an Armor-X which has been really good.

the Catalyst ones are good, and the wrist strap is handy. i'm using a Pelican one at the moment --- it's decent but bits of the edges of the case are prone to cracking off when you remove the case. i'll go back to Catalyst when the Pelican is stuffed.

for iPad a Lifeproof Nuud has been treating me well.