Water makes up a large and influential part of a fish's environment. It supplies essential nutrients, impacts fish distributions and influences fish behaviours. However, despite a large variety of established methodologies, the understanding of in-situ water flow at the scale of an individual fish is limited. We have developed a new methodology, Camera-Based Current Meters (CBCMs), to measure the small-scale flow of water that an individual fish encounters in its daily life. This method was developed to be accessible, relatively cheap and easily deployable across larger areas or at fine resolution in ecological field studies. In proof-of-concept field trials, the method successfully captured detailed flow within one cubic meter of water, resolving multidirectional and highly dynamic movement. Since fishes are likely to adjust their swimming behaviours and positions on reefs depending on flow conditions, measuring water flow at appropriate scales provides a critical new dimension to studying fish behaviour and its flow-on effects to reef ecology.