I'm looking for the name of a movie shown on HBO between 1981-1986
with the following plot points:

-The beginning of the movie has the two teens, a male and female,
landing a pontoon aircraft on a muddy river, possible either the
Mississippi or Potomac.

-About halfway through the movie, the male teen discovers a secret
spy-type command center located under a gas/service station. The
command center is accessed via an elevator which features an elevator
call button disguised inside of a Band-Aid brand first aid box bolted
to the wall.

-Inside the command center, the male teen is found and interrogated by
foreign agents, possible KGB, headed up by an actor who looks like
Burt Lancaster's Moonlight Graham character in "Field Of Dreams". The
interrogation takes place in a dark room with a bright spotlight on
the male teen.

-The ending features the teen girl defusing several bombs that are all
linked either via antenna towers or power lines. The bombs, including
a bomb underneath the very van she's sitting in, are defused when she
plays a specific set of musical notes on the touch tone keypad or
musical keyboard that she's not sure she knows how to play.

I've been trying to figure out the name of this movie for over ten
years, the only movies that I've seen that come close to this one are
1983's "WarGames" and 1986's "The Manhattan Project". Please help me
and the reward is yours!