Va. Code § 29.1-738.3
In any prosecution for operating a watercraft or motorboat that is underway in violation of clause (ii), (iii), or (iv) of subsection B of § 29.1-738, or of a similar ordinance of any county, city or town, the amount of alcohol or drugs in the blood of the accused at the time of the alleged offense as indicated by a chemical analysis of a sample of the accused's blood or breath to determine the alcohol or drug content of his blood (i) in accordance with the provisions of § 29.1-738.2 or (ii) performed by the Department of Forensic Science in accordance with the provisions of §§ 18.2-268.5, 18.2-268.6, and 18.2-268.7 on the suspect's whole blood drawn pursuant to a search warrant shall give rise to the rebuttable presumptions of subdivisions A 1 through 4 of § 18.2-269.
Va. Code § 29.1-738.3