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Water and dust proof
Although the Xperia M4 Aqua is almost half the price of the flagship Xperia Z3, Sony has kept the water-proof design with an IP65/IP68 rating that will let you safely get splashed or have fun on the beach without worrying about damaging the handset.
It's dust proof as well, so even when you're out of the water and on the sand, the M4 Aqua shouldn't kick up a fuss.
As I mentioned earlier, various ports are protected with flaps that need to be on when submerged – though the USB and headphone sockets don't need to be covered, which makes using the M4 Aqua both convenient and water proof. Thanks Sony!
The IP65/IP68 rating means that it can be submerged in water up to 1.5 metres for 30 minutes, so if you're caught in a rainstorm or pushed into a swimming pool "for a laugh", you should be fine.
Two day battery life
Sony's marketing material for the Xperia M4 Aqua focuses heavily on the two day battery life of the handset, which is certainly a hot topic at the moment.
Although two days doesn't seem like much to crow about, in a world where we're often scrambling for a charger before even a full day is done the extra day and a bit of juice could prove very useful – especially if you find it difficult to get to a power supply.
The 2,400mAh battery isn't that big, but the M4 Aqua manages to prolong battery life with a lower resolution screen, an energy efficient Snapdragon 615 processor and a range of battery saving features such as extended standby mode, which turns off apps and functions when the screen is turned off, and Sony's STAMINA mode that cuts back features when not needed.
I'll go into whether or not the M4 Aqua's battery life lives up to Sony's promises later, but there's no denying that if you're sick of your smartphone struggling to last a single day, the promised two day battery life on offer here is very tempting.
Large and vibrant display
The Xperia M4 Aqua's 5-inch screen is another big selling point, and as with other Xperia devices, Sony has put in some tricks and hardware that it picked up creating displays for its Bravia range of high definition TVs.
Although the screen's 720p resolution doesn't reach the heights that more expensive flagship phones usually ship with, Sony has done an excellent job of ensuring that it still looks bright and vibrant, and unless you compare it side by side with a handset that packs more pixels per inch, you'd really be hard pushed to complain about the screen.
The IPS panel also provides excellent viewing angles, so you don't have to stare at the screen dead on to see what's being displayed.
If you want to huddle around the phone to catch up on your latest Netflix obsession with some close – and I mean really close – friends, then their viewing experience won't be badly impacted by viewing the screen at an odd angle either.
The large 5-inch screen and 720p resolution leads to a pixel density of 294ppi (pixels per inch). The Xperia Z3 by contrast has a 5.2-inch screen with a 1080p resolution for 424ppi.
The more pixels per inch the screen crams in, the sharper the image quality, but that doesn't mean the M4 Aqua's screen is fuzzy – in fact I was very pleasantly surprised by the image quality of the screen (thanks to Sony's display tech); pixel density be damned.
Not only does the screen look good, but it's fast and responsive to touch gestures and the scratch-resistant glass proved very resilient. Combined with the waterproof design, the M4 Aqua feels like a robust smartphone you'd happily take out and about with you.
