You can send all ETH into Waves.  It just goes through a gateway.  The gateway stores all incoming ether in 1:1 ratio, then issues you corresponding wETH tokens on Waves Platform.  You can then trade those vs any pairing on the DEX within the Waves wallet.  wBTC/wEURO/wUSD/WGR/MGO/MER/RBX/STA/PBT and so on.  You also have fiat gateways.  But yeah, you can send the wETH to any other Wave's account via their Wave's Ether address...or if you wanna cash your wETH back out , you just send it to your myetherwallet for example, and it goes through the gateway, and bingo you have your ETH again in myetherwallet.