This page of the Mafia Definitive Edition guide contains a walkthrough for the Explosive Situation side mission available in the Free Ride mode. You will learn how to drive the marked vehicles into the water and how to complete the challenge within the time limit.
You can learn about this mission by finding Herbert Baskerville's letter in the Free Ride. The letter is found in the hallway on the upper floor of Salieri's bar.
It has information on where the mission will begin. This telephone booth is adjacent to Pepe's Restaurant in the North Park district.
Choose a fast and easy-to-drive vehicle for this mission. This will make it easier to get to the first out of the three cars marked by the game.
It's one of the more difficult side missions. You have 7 and a half minutes to complete the task. However, that isn't a lot because you have to reach 3 different vehicles and drive each one into the water.
We recommend starting with the vehicle marked as 1 on the above picture – it is located the farthest from the starting point. If you make mistakes in the initial part of the mission, you will be able to restart it immediately. The recommended area for sinking cars is also highlighted in the image – it's Waterfront in the Downtown district.
After finding each vehicle, try to reach the narrow street in the Waterfront – see the pictures. That street ends with a ramp.
Gain more speed. If you drive fast enough, you'll land in the water right away. Otherwise, you will end up somewhere next to it – in that situation, get to the small pier quickly and drive into the water.
Tommy won't die after falling into the water. The main character will respawn on the shore after a while – you will be able to continue the mission.
After drowning each of the cars, start sprinting towards the nearest road. If you are in the recommended area, you will reach the road by following the stairs shown in the picture. Quickly steal a parked or a moving vehicle. It would be good to choose a slightly faster machine, but don't waste too much time looking for a new car.
The reward for completing this mission is a boxer outfit. You can wear it by interacting with the wardrobe at Salieri's bar.