............. You are quite correct in you're assumptions here, CJ left the clues to the reader, Bridget concluded it had to have been a bomb based on what she saw in the water. She saw what she thought was scorched pieces of the boat along with the zodiac. She extracted the few pieces and left no trace. Gonzales based his assumption on the report that the Ares was missing and found no wreckage, and the divorce proceedings. Rachel's distress call made no sense otherwise, she could not have known a bomb was getting ready to explode, so it was all a ruse for her to get away. Leaving litter in the ocean, letting the authorities to beleive she was dead and lost at sea, she sailed off. The big question is why? Did she discover Arnold's secret compartment and realize that she and her family was at risk? I think the latter is correct and as much as it hurt Trevor she had to make herself invisible to protect him, the 7 year was to bide time and maybe money to resettle Rachel.
BTW, nice to see you here, enjoy your stay!!