Purchase land under a lake or river?
Likely cannot buy it.
There are people who retained title to their land in the flood margins of the Missouri River lakes when the dams were built. They came under considerable pressure to sell to the Government, but a few held out. Damned few. The Corps of Engineers controls the shorelines and bottom under those lakes (Ft. Peck, Sakakaweja, and Oahee), to the point that even those who still own the old but submerged homestead sites cannot walk out there when the water is low and pick up stuff that remained when the family moved, or they will be found in violation of some Corps antiquities regulation.
So, it is possible to own that land, and the mineral rights thereto, but the Corps has control if it is below the high water mark. Mineral rights can be leased by the owners if they were retained, because horizontal drilling has made it possible to tap those resources from well on shore, back off Corps Land. As far as I know, the title to that land can be transferred, just the same as any other land, but usage is severely restricted, depending on the relation of the land to water level.
The pipeline crosses the ranch the pipeline operator purchased, the Tribe has no control unless an injunction is granted on the basis of 'cultural assets', and their attempt to seize control through those means has failed.
Not only have no cultural assets or burials been found in prior excavations and surveys, the Tribe made no apparent effort to obtain title to this land they suddenly deem "sacred". The only remotely valid concern raised is one for water supplies, but that would require a problem with the pipeline itself, and in the stretch where it crosses the water or close enough to that to contaminate the water. I have little doubt that all will be rigorously inspected and meticulously emplaced to avoid such problems.
Still, the Obama Administration is delaying approved construction by requesting a 'voluntary' (like the income tax?) suspension of activity.
With the understanding that the pipeline will have the takeaway capacity of nearly half of the production of the Williston Basin (including the Bakken and Three Forks) at peak, it is highly likely that every Environmental and other organization (often with no connection to the State or the area) who can will throw a dog into the ring, will, to hold up the project for a "settlement" (blackmail).
Not only is the investment enormous, but the loss of potential revenue is as well, and delay only makes things worse for the pipeline company.
