To find the tee for this first 'extra' hole after #16, head straight back into the woods behind the 16th basket. The tee is next to the channel at your left about 100ft back in the woods, and the hole parallels the channel.
Easiest/safest way to play this intimidating hole is to send your tee shot onto the big "island" with the basket for hole A as a shortcut, then send a long second throw across the second channel and land near the basket. It takes a good bit of extra walking, but is reachable in two throws that way.
The tee is just back into the woods behind and to the left of the basket for #16. It plays back towards the 16th tee to the basket on the "island"/peninsula, in other words not from the 16th tee across the water.
If you have the arm for it, you can shortcut this hole by flying over the moderate-height trees along the street and over the road, then dropping back leftward in to the green (short) basket. That can be a lot easier than hitting the low ceiling tunnel under the large oak tree.
New extra basket (yellow band) is located above the drainage ditch near the road bridge but across the road, probably 100' or so long of the regular pin. You can see it from #8's long pad.
A new extra basket (yellow band) is located on a point about 100' right and slightly back of the original straight ahead position. Also a new mando (red arrow) on the first tree on the right off the original tee to protect pedestrian bridge.