Nature explorers want to blend into the scenery so they don't startle the wildlife and can observe it close up. We've found that breeding seagulls don't attack when we wear the hood up. They don't see us as a threat when we sit silently in the bushes or lay submerged in the water.
A poncho or hiking cape is airy, lightweight, and easy to swim in. It hides your shape so you look like something that just floats by, not like a predator. The trapped air in your poncho creates a random shape.
Most animals can't see in colour, but can quickly recognise shapes, patterns and movement with much higher precision than us.