Hi Aura,
A friend of mine had one and she loved it for around a month then was sick of it. The biggest issue was that theres not much fun in having just one - you need someone else to have one as well. She used to invite people out for a 'go on the jet ski' of a fine evening, most friends went once then gave up as it was boring to sit and wait all evening for a 10 minute turn on it with 20 other people waiting also.
She also found it hard to find nice places locally to use it (she was living near dublin city centre at the time), as it was a bit of a trial having to load it up onto a trailer to move it about.
After she had it a year or so (spent most of that year in a shed gathering dust) it was stolen, she never bothered taking an interest again and reckoned you can have the fun without the hassle by renting one when you need it.
There may have been an insurance question on it too - you would need to look into that.
She had bough it based on enjoying using them on holidays but failed to factor in Irelands weather and potential for fun in an ice cold sea.