[en] Contactless power transfer system having a primary 60 and secondary 64 element. Between the primary and secondary elements there is at least one field focusing element 92/94 and a partition. The system is disposed within pressure isolation cavities 76/78 of a subsea assembly. The system may be within a non-conducting magnetic shield. The system may also transfer data. There may be one or more resonators having unique resonant frequencies. Further independent claims concern contact powerless systems not specifically for subsea assemblies / without pressure isolation cavities but further specify differing resonant frequencies and filters.