Wave energy devices traditionally tend to be large, as their sizes are often determined by power conversion targets and their operating wave climates. Here we examine a size-constrained device designed to fit within narrow tubes, and using well-known analysis techniques show that converted power amounts may be large enough to meet or exceed the needs of instrumentation to serve a majority of oceanographic and defense ocean measurement needs. The device examined in this paper is designed to fit within, and to be deployed from, torpedo tubes or other equivalently sized cylindrical containers. Examined in this paper is a traditional tubular oscillating water column device, and particular interest here is in designs that lead to optimization of power converted in anticipated wave climates. A two-step design procedure is investigated here, wherein a more approximate two-degree-of-freedom model is first used to identify relative dimensions (of device elements) that optimize power conversion from relative oscillations between the device elements. A more rigorous mathematical model based on the hydrodynamics of oscillating pressure distributions within solid oscillators is then used to provide the hydrodynamic coefficients, forces, and flow rates for the device. These results are next used together with a power take-off model, to provide a quick but rigorous way to estimate the energy conversion performance of the device in various wave climates. A power take-off based on a self-rectifying turbine system is used, and its representative conductance and susceptance values are derived for a chosen geometry and configuration. Calculations are carried out to illustrate the design procedure, and converted power values exceeding ten watts are noted in wind-sea like conditions. Further, performance comparisons with solar panels in Arctic latitudes indicate that such designs may yield considerably better energy conversion during seasons of low insolation. These devices could be designed to convert enough power to perform designated ocean measurement operations while storing any excess energy to support vehicle recharging operations.