Double-pulse LIBS is a promising technique for underwater material exploration. Since this has barely been investigated for deep-sea applications, measurements in pressured water with up to 600~bar were done, to show the usability. For this, a double-pulse system with up to 150~mJ each laser pulse was used to find a setup which allows to identify separated spectral line emission from plasma even at elevated pressures. For this, spectral parameters were determined and the influence of laser pulse delay, the trigger time of the spectrometer and the laser pulse energy on these parameters were examined. It was found that a very short pulse delay of 0.5~μs and skipping a few hundreds of nanoseconds after the laser pulse for the measurement are necessary. Furthermore, small laser pulse energies are advantageous for consistent results in the entire range of hydrostatic pressures of up to 600~bar.