Blue Water Navy Vietnam Veterans Act of 2019 This bill addresses certain health benefit and home loan programs for veterans. Specifically, the bill extends the presumption of service-connection for certain diseases associated with herbicide (e.g., Agent Orange) exposure to veterans who served (1) offshore of Vietnam between January 9, 1962, and May 7, 1975, or (2) in or near the Korean Demilitarized Zone between September 1, 1967, and August 31, 1971. Under a presumption of service-connection, specific disabilities or diseases diagnosed in certain veterans are presumed to have been caused by the circumstances of their military service. Health care benefits and disability compensation may then be awarded. The bill extends eligibility for health care, vocational training and rehabilitation, and monetary allowance to children with spina bifida who have at least one veteran parent who may have been exposed to an herbicide agent while serving in Thailand between January 9, 1962, and May 7, 1975. The Department of Veterans Affairs (VA) must report on the Follow-up Study of a National Cohort of Gulf War and Gulf War Era Veterans. Additionally, the bill revises the VA home loan guaranty program to adjust loan fee rates and eliminate the limit on the amount of a loan for which the VA may provide a guaranty of 25%. Under current law, these loan guarantees are subject to a limit on loan size determined by Freddie Mac. The bill removes the cap on a direct housing loan amount that may be made to a Native American veteran purchasing a home located on tribal land held in federal trust. The bill also waives loan fees for active duty Purple Heart recipients. The VA shall permit a VA-approved appraiser to make a housing loan appraisal based solely on information gathered by a person with whom the appraiser has entered into an agreement for such services.