A tsunami, the tidal wave, can not be seen in the open ocean. There is just a swell that isn't noticeable. As it approaches a shore line the volume of water begins building up as the bottom gets shallower. Frequently, shortly before the wave comes ashore, the water begins to recede.
A man shows up at the police station, goes talk to Friday, pulls out a gun, points it to his own forehead and threatens to kill himself unless they let him talk to the police chief. Friday convinces him to give him the gun and then they go on about doing business sitting together, instead of arresting the guy.