My strategy for writing this autobiography is to use examples of how working on seemingly different projects can often lead to outcomes more important than originally envisioned. Serendipity is a happy accident-specifically, the accident of discovering something useful without directly looking for it. This often occurs when two research projects converge unexpectedly. The main text contains examples of how serendipity has led me to important discoveries, including (a) finding surprisingly high 228Ra activities in the ocean; (b) developing a means of rapidly and quantitatively extracting radium from seawater; (c) devising a rapid, sensitive method of measuring 224Ra and 223Ra; (d) realizing the scale and biogeochemical importance of submarine groundwater discharge; and (e) conceiving a method to estimate the total flux of submarine groundwater discharge to the Atlantic Ocean. The Supplemental Material fleshes out details of these discoveries and places them in the context of my other investigations.