Like all Totems, it cannot move, and its health will slowly deplete over time, disappearing upon it reaching zero. Summoning another Water Totem will not remedy this, as it cannot be healed by another Water Totem.
Having low health, they die with few hits from enemies, so placing them behind the other units is essential to keep them protected. It is recommended to always summon a second Totem before the first expires. Also, the healing stacks, meaning that summoning multiple Water Totems will result in successive healing waves.