"A fertile spot in a desert, where water is found."
|Sky view of Oasis|
Compare that to Oasis Visitor Center.
It's a refuge in the middle of a swamp surrounded by water on all sides.
|Ground view of Oasis|
from the parking lot
Or, at least that's usually the case;
First the summer rains have to return and fill it back up.
Until then, yes, it's a seasonal oasis in the middle of a desert-like swamp.