Sony has an interesting problem on its hands. For one thing, most companies tend to launch their flagship phones at MWC, but Sony is going for the mid-range with its new M4 Aqua.

Some technology pundits assumed there would be a Z4 announced at Mobile World Congress, but that hasn't been the case. This is largely because Sony is slowing down its release schedule, and moving toward one flagship phone per year.

The M4 Aqua is designed to do two things. Firstly, it's a sensibly-priced handset with plenty of features, and secondly it's waterproof, hence the name.

Sony is, it seems, pretty proud of its waterproofing, and so it should be. It has pretty much led the pack on making premium handsets that are also rugged, and from IFA last year, we know that it's working at making its handsets even tougher, too.

Like the other Aqua-branded phones and the Z3, Sony lets you dunk your phone in one metre of water for up to 30 minutes. That's great for people who have dropped their phones in the bath, toilet or bidet. Sony has also designed the M4 to not need a USB protection cap, which is handy.

The whole thing is powered by one of Qualcomm's Snapdragon 615 processors, and it has 2GB of RAM to help keep things moving. It's also 4G ready, which is great for those who yearn for faster downloads.

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But another strong area for Sony is camera technology. The M4 Aqua is also being billed as a way for people to get into mobile photography at an affordable price, and although it doesn't have Sony's amazing 20.1-megapixel camera, it does instead boast a 13-megapixel shooter. That said, the work Sony has done on low-light performance is what matters here.

Oh, and the price isn't bad either. It's expected to be about £300 when it launches, perhaps even slightly less. That puts it on a par with some great handsets, like HTC's One Eye and Microsoft's Lumia 830.