Flying boats - Step goes at or slightly behind the CG.

Easiest water rudder is an air rudder that extends slightly below the water line, with a small ventral fin protecting it. Make the hull either flat bottom, or very shallow v-bottom. Hull size is dictated by the floatation you'll need.

High tail locations can help (horiz stab). T-tails are common. Low stab can be difficult to get prop wash over the elevator for the take-off run.