Groupon is the best way to go, for what you will pay for one person you can pay for two through Groupon
You can bring your own rope to tether. Check groupon for discounts.
$30-$45 depending on time selected plus $7 for parking, plus $3 if you want them to hold your keys, plus $2-$4 if you need to tether your tubes together.
Between $30 to $45 depending on the tube you take
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