Paul here from Onboard. Got this via Google alerts :-)
We do the standard rides, half hour and hour, out of Gunwharf with the public but if you wanted to take the boat exclusively mid week in particular or something I am sure we can work out an equitable figure for you too. If you email me direct on firstname.lastname@example.org
with requirements I can tailor it to suit for you.
Round the harbour will obviously be cheaper fuel wise too rather than blasting to the needles and back in the time.