Coupling of gravity deployed Ocean Bottom Seismometer multicomponent sensors has been an issue for at least 30 years, and remains largely an empirical art rather than a science. There are a number of reasons why it retains it elusive nature ;- the environment is generally hostile and all operations have to be conducted remotely, the nature of the seabed is highly variable from place to place, so that it is impossible to directly compare results from different sites, but largely because making detailed in-situ comparisons of a number of sensors accurately deployed in controlled deep sea conditions adjacent to each other is extremely costly. This paper considers some of these problems, and ways in which coupling can be evaluated in the laboratory, and the limitations that result. Variations of the internal sensor geometry also affect the sensor response in deployed sensors.