Gary used to charge us around 60 euros for a 10hp boat out of Arillas for the day. It will be around the same from San Stef if the guys are not back in Arillas this year. We tend to go south as there are loads of bays and coves to stop, snorkel and take lunch. We used to do the full day, 10am-6pm and used around 25-30 euros of fuel which you pay on your return. The boats normally take 4-6 adults. As for snorkelling, yes it isn't great from the beach, but if you go to the far end of the south beach and snorkel from there it is much better with more rocks and sealife.