I dare say that your ski is just letting you know that it's due for a service.
Start the jet ski and reset the maintenance reminder. On my 04 Xpdi you have to press and hold the set button for a few seconds. Yours may differ but I would try that. You may need to look in your manual if that don't work. That should reset it.
If the maintenance light and or buzzer comes on whilst your riding it means that there is something wrong with your ski.
I just had the same problem and I read that you have to push on hold the set button for about 3 seconds and it has not come back on. If it comes back then it is a trouble code.