Yes, if you have a separate hot water cylinder connected to your heating system (also known as a conventional heating system) you can control your hot water with Hive. Hot water can be controlled within the Hive app by selecting Hot Water in the app dashboard or the all devices list in the top left navigation. It can also be controlled from the Hive website when logged in and manually with the thermostat:
Hive Active Heating™ 1 thermostat: via the < button
Hive Active Heating™ 2 thermostat: via the 'Menu' button
Control of your water temperature is not supported by Hive Active Heating™. You can turn your hot water on or off, set a schedule or Boost it, which turns the hot water on for 1-6 hours.
You can usually set the temperature of the hot water directly on your cylinder.