Koopa Beach 1
From the Super Mario Wiki
Koopa Beach 1 is the first course of the Star Cup in Super Mario Kart. It is a very short course, and takes place on a set of small islands. Its hazards consist of Cheep-Cheeps and green 'rough' sections of the beach which slow karts down. Karts can drive through the light-blue shallow water, which will slow them down a bit, but will sink if they go into the deep dark-blue water.
There is an extra Item Box a bit off the track, which is quite easy to reach.