Now Playing: Gusts send outdoor furniture flying

Now Playing: Maria forecast to intensify to Category 4 'dangerous major hurricane'

Now Playing: Kayakers' close encounter with whale and her calf

Now Playing: US conducts military exercises amid tensions with N. Korea

Now Playing: Russia's war games on Europe's doorstep

Now Playing: Hurricane Maria strengthens to Category 4

Now Playing: A koala was rescued after being trapped in a car's wheel arch in Australia

Now Playing: Aerials from scene of London incident

Now Playing: Scotland Yard calls for vigilance in wake of London train explosion

Now Playing: Witness describes 'haunting images' of London train explosion

Now Playing: Russia starts big war games along its border, alarming its neighbors

Now Playing: UK prime minister on Trump's London attack remarks

Now Playing: Terror in the UK: A timeline of recent attacks

Now Playing: Restaurant gives slice of kindness to London first responders

Now Playing: Children in London discuss London terror attack

Now Playing: Man tries to drag beached shark back to sea

Now Playing: 'The Briefing Room': London terror attack

Now Playing: London commuters speak out about bucket-bomb explosion

Now Playing: World's oldest giant panda dies at 37

Now Playing: Japanese sirens go off after North Korean missile launch