Freestyle 180° or 270° reverse turn You'll need to understand well the backhop. It starts the same, with a twist from the waist while lifting the front wheel.

A classy unexpected move
First, align yourself as close as you can to the side you want to jump. The tires should be virtually on the edge, or standing on the last three inches of border.
1° Pull on the bars for a backhop, and give a strong twist like trying to look back. Turn inwards.	2° Once in the air, carry on the turn by realigning the bike with your shoulders.	3° The move continues, past the realignement of the bike with your body to complete the turn.
Land with the back wheel first, that lets you more flexibility for the finish. See the move in a video

270° turn

315° turn

270° landing in water