There's no shortage of power in the marine environment, but how do we turn it into something we can use? And how can we measure what's happening in this energetic environment when water and electronics generally shouldn't be mixed? A quick tour of wave and tidal power, and how we can measure the power available at sea - including some examples of how that works (or doesn't) in practice from prototype testing and research. Featuring specialised instrumentation with a hefty price tag, some rather more DIY Arduino and Raspberry Pi solutions - and reluctant use of a grappling hook. Examples drawn from work carried out while employed at Swansea University, with permission.