Something for ocean currents...

[Punky]

Now that would be a challenge! Trying to take pictures in a
current.
You would have to have a buddy willing to help stabilize and
protect you from being pushed into coral or plants so you could focus on your shot.
That jon line sounds like it would help from the ascent/descent
line. My concern when you talked about holding on was waves jerking you when the boat rode up on one.