Unfortunately your daughter will not be able to stand up as she enters the sea as there is no beach. But both my 13 and 11 year old managed to get in OK and the younger one is not a strong swimmer. He couldn't get on with the snorkelling as he didn't like the mouth piece.
She might be better off just going in for a swim first without her snorkel to get used to it and get her confidence up.
There are two Jettys that you can enter the sea from at the Crowne Plaza most people seem to take a liking to one and stick to it. They wobble a bit but loads of kids went in. I watched mine from where the sunbed terraces were, but my OH went in with them often as he loved the snorkelling.
There is a courtesy bus. It went in to early for us, about 5pm. We got one of the CP's own taxis in, they are outside reception on the left are pale grey and plentyful. Wished I'd asked him to come back for us, but that's difficult as your not sure how long you are going to be.
My son loved the blue and white taxi back as it went so fast he thought it was like being in a grand prix.
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Didn't do the quad bikes so cant feedback on that one.