A closeup of an individual flower would be nice. But, it looks like you don't get one without wading in the river. But that would be a small sacrifice for art :wink-new:
My shooting buddy has a new Canon EOS 5D Mark IV along with a fancy $2,000 lens. He went with me on the shoot and he brought waders and went about 1 third of the way across the river (it is shallow) he hit a slick spot and went down. The camera went under water. It quit working about 5 minutes later. He did get the camera back working the next day and the AF on the lens was still hosed. About another day of drying it finally started working.
So NO, I and not wading out into a river with my d750.
I am going back on day next week with my Tamron 150-600 and get a few closeups.
Heading to a alligator farm tomorrow that has a active heron rookery over it.