A liquid handling system transfers liquid (e.g. water, bearing marine animals) between two tanks each having a respective liner which is movable between a lining position (when filled with liquid) and an inverted position (when its respective tank is emptied). In an initial state, liquid is held in a first tank. By supplying air to a space between the first tank and its liner, its liner is progressively lifted and liquid passes along a channel onto the initially inverted second liner (which acts as a baffle to slow the liquid flow). Air in a space between the second liner and the second tank is vented so transferred liquid sinks the second liner to fill the second tank. A ballast liquid may be used in the spaces. Initially held in the second tank, the ballast liquid flows via a passage into the first tank as transfer of liquid progresses.