You should look for Google Chrome extension for Waves. That one is official and working quite nice. But you should always backup your private keys and pass.
If it's an offline wallet why do I need G Chrome?
Couldn't I download it without Chrome?
yes use the github download it will download the full version that can be use offline.
https://github.com/wavesplatform/WavesGUI/releasesthe chrome link is for in-browser wallet, it's a chrome extension that can't be used with other browser