Dwayne tells JP to check the scuba tanks to see if the divers all used the same amount of oxygen. Scuba tanks are not filled with oxygen; they are filled with normal air.
The Commissioner tells Humphrey that word has reached him that a wealthy tourist has been killed. Earlier when Humphrey is interviewing the suspects, it is stated that Dan, the victim, lives on the island. However, the person who reported the murder might not have known that Dan was a local.