Level :
The level would be a classic water/beach themed demon with fast paced gameplay and a song that slowly builds up.
Jetski mechanic :
This is basically a custom gamemode where you are a jetski surfing on the waves.
There are 2 states in this mode : surface and under the water.
When you are at the surface, if you hold, your icon will go down as long as you hold. It will cancel your momentum if you were going up and send you down exponentially. If you dont hold, your icon will slowly fall on the water and then keep moving in a straight line.
When you are under the water, your icon will go up very fast exponentially. When it reach the surface, it will go more or less high in the air depending on the momentum you gained while underwater.
Introduction :
The level would start like a normal level. Before the drops, there will be indication to how to play the jetski mode. It should be IN the decoration so maybe something like a big sign on the sand with "HOLD TO DIVE / RELEASE TO PROPEL" with the jetski icon drawn doing the 2 actions.
And then when the drop hits, the jetski gamemode would start. If the level has multiple drops, the jetski mode will be used multiple times to represent the energy of the song.
The first jetski part will remain simple and easy to learn, allowing the player to quickly understand the mechanic even at higher difficulty.
Impact :
The gameplay will alternate between normal gameplay in slow or mid paced parts, and every drop would have a jetski part. During these sections, the player constantly alternates between diving to build momentum and releasing to launch in the air, creating a rhythm based loop of dive, launch.
Why it's good :
Jetski mode add a new way to control vertical movement and introduces a momentum based playstyle, which creates a more dynamic experience compared to standard gameplay.