SURVEYS ON NAVIGABLE STREAMS.
Tex. NAT. RES Code § 21.012.
in effect(a) If the circumstances of the lines previously surveyed under the law will permit, land surveyed for individuals, lying on a navigable stream, shall front one-half of the square on the stream with the line running at right angles with the general course of the stream.
(b) A navigable stream may not be crossed by the lines of a survey.