When the robbers are cutting into the bottom of the ocean liner we see from one angle looking up that they are many many feet above the ocean bottom. For the same scene when we see an angle looking down one of the robbers is clearly kneeling on the bottom of the "ocean" (really just a studio tank).
Officer Luca asks the art teacher, "Have you seen two guys and a girl?" implying there are three people. But then Luca says, "Those four people are probably in a big hurry!"
Although Lieutenant Dan 'Hondo' Harrelson's wife and family are never shown in season two he is presumably still married as there was no mention of death or divorce. It was established in his backstory that he was a dedicated family man so his apparent romantic interest in women he meets in season two is out of character.