Agent Orange

If you served in-country in Vietnam and have been diagnosed with
Leukemia
Diabetes
Hodgkin’s disease.
Multiple myeloma.
Non-Hodgkin’s lymphoma.
Prostate cancer.
Respiratory cancers (cancer of the lung, bronchus, larynx, or trachea).
Soft-tissue sarcoma (other than osteosarcoma, chondrosarcoma, Kaposi’s sarcoma, or mesothelioma).

Then you are eligible for a VA service connected disability payment.

Some shipboard service might count as in-country if you operated in coastal or inland waters. Having anchored in DaNang harbor would be considered operation in inland waters, for example.

You can get help applying for VA benefits from most Veterans Service Organizations.