The deep Slocum Glider "WILLY" is seen at the sea surface as it transmits data wirelessly. WILLY is performing a series of tests, diving in steps from the surface all the way down to 600-1000m in order to pressure-test the hull. IMEDEA: Instituto Mediterráneo de Estudios AvanzadosTMOOS: Tecnologías Marinas, Oceanografía Operacional y Sostenibilidad.Location: North Coast of Mallorca, Spain