One of the best things about the M4 Aqua is that it doesn't look or feel like a mid-range smartphone. You could easily confuse this with the flagship Xperia Z3 since it has all the same style and design traits. You do notice the plastic edging (rather than metal) when holding it and the glass rear cover doesn't sit entirely flush with the edge at the top and bottom. Neither are big issues and the phone pulls off the premium look at half the price extremely well.

With the M2 Aqua, Sony brought the dust- and waterproofing which was previously reserved for the high-end Z range to a cheaper smartphone. It's got an IP68 rating which is the highest available and along with the Xperia Z4 Tablet, now the microUSB no longer requires a fiddly flap. There are separate flaps for the SIM slot (Nano SIM) and SD card slot.

We like the size of the M4 Aqua since it's not too small and not overly large and therefore a handful. It will feel comfortable to most users and the Xperia M4 Aqua is very thin and light for a mid-range phone at 7.3 mm and 136 g. It will be available in black, white, silver and coral.

This is Sony's first smartphone with a Qualcomm Snapdragon 615 octa-core (quad-core 1.5GHz Cortex-A53 & quad-core 1GHz Cortex-A53) 64-bit processor and there's also 2GB of RAM, 8GB of internal storage and a microSD card slot (up to 128GB). Not bad for the asking price but it's worth noting that you'll need a memory card as there is only just over 1GB of available storage out-of-the-box.

Performance is perfectly good for a phone of the this price. It's smooth most of the time with only really the camera which takes a bit of time to load and that's mostly the first time you load it. As you can see below the Xperia M4 Aqua outpaces the pricier Galaxy A5 in three out of four benchmark tests and beats the Honor 6 in the graphics departments with its lower resolution display. None of the results are particularly impressive but as we've said, there's no issue with performance here.

The screen has jumped from 4.8in with a qHD resolution to a larger 5in IPS display with a 720p HD resolution. You're getting a decent screen for a mid-range smartphone with a pixel density of 294 ppi. There's good colour reproduction, brightness and viewing angles on offer here. We'd like Full HD in terms of resolution so look elsewhere (namely the Honor 6) if this is a must.

There aren't really any other features to mention such as wireless charging, an IR blaster, fingerprint scanner or things of this nature. Sony really focuses on the photography, battery life and waterproof design. There is NFC, Wi-Fi and Bluetooth 4.1 on-board, though.

As per usual on Sony phones, the battery is hidden away under the shiny exterior and you can't access it. Although there's no wireless charging, keeping the Xperia M4 Aqua topped up is much easier now thanks to that waterproof USB port. Sony touts a two day battery life, like it does with premium Z range devices and we've found this to be true. The combination of a Snapdragon 615 processor and a 720p display works out well for energy efficiency. There's also Sony's excellent Stamina and Ultra Stamina modes if you want to push things even further.

In our battery benchmark, via Geekbench 3, the Sony Xperia M4 Aqua lasted four hours and 49 minutes with a score of 1932. That's similar to the LG G4 which lasted four hours and 44 minutes with a score of 2841.

Mid-range smartphones tend to scrimp on photography but the Sony Xperia M4 Aqua has a 13Mp rear facing camera with Sony's Exmor RS sensor and a 5Mp wide angle lens snapper at the front for selfies. Sony is one of the only smartphone makers still offering a dedicated physical button for the camera and long may it continue. You can launch the camera at any time, half press for focus and fully press to activate the shutter. Like many smartphone cameras, you don't get all 13Mp as standard because it's set to shoot in 16:9 to match the screen. You'll get 9Mp unless you switch to 4:3. The camera shoots at up to Full HD so if you want 4K video, you'll need an Xperia Z for this.

We've found the cameras able to provide decent quality results with the Superior Auto Mode handling most situations really well but there is a Manual mode if you fancy switching it up. There's HDR as well as various camera apps like Sweep Panorama, Sound Photo and AR fun. Although the Xperia M4 Aqua will take decent snaps to show off online, it can take a little while to focus on a subject properly which isn't ideal when shooting moving objects such as children or pets.

Like the Xperia Z4 Tablet, the smartphone runs Android 5.0 Lollipop which is the latest version with Sony's own user interface which this time around uses many stock Android elements like the recent apps menu and dropdown notification bar. For the better, Sony has kept it's little floating widgets including a calculator which are accessible via recent apps. You can also select which Quick Settings you want which is not a part of stock Lollipop.

We found the software to be smooth during our time and we like the fact Sony hasn't gone mad with customisations. This means there's little to talk about beyond the usual selection of nice wallpapers and widgets - although you can download Themes which change the look and feel of the interface if you want.

As per usual, Sony pre-loads its own apps such as Walkman and PlayStation but you'll have to opt for a Z2 or Z3 handset if you want features like High-Res audio support and PS4 Remote Play. Things are a little more basic on the M4 Aqua. There are a number of pre-loaded apps including Vine, AVG, OfficeSuite, Sketch, TV SideView.