Haven't been boating into the Grand Canyon in quite a few years and the last time I got to about point "A" (attached map)
Now, all the high resolution aerial photos show little water east of Sandy Point. Has anyone been in there lately? Seems there would have to be enough water for a shallow draft vessel?
I've done the trip many times and the last several years haven't been friendly to those of us who like to head up the canyon because of the water depths.
Earlier this year you could have done it, but now I would be hesitant to without a jet like a North River or something similar. Some friends of mine went up earlier this year when the water level was up past 1130, but at 1115' it's down 15-20' since their adventure. They went pretty much right where your mark is too, and only hit 1 sand bar.
I'm looking forward to being able to head up next year or the year after, depending on how much precipitation the Rockies get. I think the Google maps that have been updated are showing the lake at it's higher elevations earlier this year.