For now, I think the best solution is to ask around to see if anyone would be willing to lend you theirs (lecturers/teachers/students), or buy another one.
The first step would be to remove the batteries, and let the device discharge by leaving it alone and/or pressing the power button a few times. Then replace with brand new batteries.
As for an actual repair, you’ll have to pry the device open (carefully) to have a look at the electronics inside and determine if there is any actual water damage.