Fig. 6: Cruise ships.

Spectrograms of ultrasonic antifouling signals recorded from seven individual cruise ships from five different cruise lines, including the vessels a Koningsdam, b Carnival Miracle, c Oceania Regatta, d Navigator of the Seas, e Royal Princess, f Grand Princess, and g Majestic Princess. The recorder used for the Royal Princess had a 96 kHz sampling rate, and the recorders used for all other vessels had a 576 kHz sampling rate.