From the Super Mario Wiki, the Mario encyclopedia
Tropical Coast is a race track in Mario Kart Arcade GP DX. This track appears as the 2nd and 4th rounds of the Mario Cup, while Splash Circuit appears as the 1st and 3rd rounds of the same cup. The layout of this track is generally the same and based off Mario Beach from Mario Kart Arcade GP and Mario Kart Arcade GP 2; but the theme of the track is significantly different from the two games.
This track starts off straight, but instead of turning right, they go down which leads to another path. The players go down a big slide which leads to the underwater section. After that is a sharp curve to the right. After a short while, the racers will turn right into the cave. After a while, the racers will make a slight right turn, slight left turn, exit the cave and climb up via Dash Panels to the sandy area. Upon reaching the sandy area, the track joins the Splash Circuit path, which is halfway of that course. They will be on the right side of the split before the paths join together. After the sandy area, the karts cross the Mario Kart sign and make a right turn which is final turn of the circuit. This turn will lead the drivers to the finish line. The racers do 3 laps in this track to finish a race.
Various signs appear in this course. Some of these signs are also seen on Splash Circuit. When the racers go underwater, they will see a sign that says "Welcome". The ship appears in front of the Diving sign and above the entrance of the underwater section.