Sand sediments are a ubiquitous feature of our coastline, and often contain high populations of microalgae, such as diatoms. The dynamic nature of these sediments means that these microalgae are often mixed into deeper anoxic sediment layers for timescales of hours to days. Surprisingly, there has been very little research on algal metabolism, once in this environment. Our recent work suggests that fermentative pathways dominate, with high rates of hydrogen and lipid production. Here, I will present findings from some recent studies on the types of lipids formed and high rates of hydrogen release into the sediment and water column. These findings suggest the conventional view of sediments being dominated by anoxic bacterial metabolic processes may not be applicable to sand.