Swale

Golf is a difficult game and you are sometimes faced with huge obstacles in this fruitless pursuit of getting a small white ball into a tiny hole. When playing a new course we are helped by reading a description on the hole diagram which is supposed to help us plan our approach to the green. This description does not help if the green is protected by words you've never heard of. The 16th at The 500 Club has one of these:

From an elevated tee, avoid two fairway bunkers 150 yards from the green. The second shot can be tricky with four bunkers and a swale surrounding this shallow, undulating green.

What is a swale?

Well it turned out to be a grass bunker. Earlier, hole 5 (Quail's Trail), had grass bunkers and they called them grass bunkers:

This testy par 3 requires a high tee shot to a green surrounded on all sides by grass bunkers. This green is deceivingly contoured. Par is a very good score.

So why call it a swale when it's a grass bunker?