Walindi Plantation Resort and MV FeBrina recommend the following Spanish agencies, listed in no particular order.  The country code for Spain is +34.

Ultima Frontera
Contact: Ramiro..
C/- Francisco Gervas, 17 7oH, 28020 Madrid
Tel: + 34 91 571 8470/ Toll Free:

The reefs are pristine and offer what I assume is diving as it was 100 years ago. The bonus was Orcas on the last day, something that I will not soon forget.

Travellin-Tireman, Canada (Trip Advisor - June 2014)