I did the trips in March (27th), May and June last year (1st and 8th) and the route seemed quite different. I recall going around Lamma island only once in those tours, when we saw the Roseate terns on a floating post (and the tour around Lamma island was uneventful too). However, even then, the boat didn't simply go straight from Po Toi to Lamma and longed the coast for one hour or so.
I just mention the routing this time, as I felt it may not have been adequate, based on a few trips I did before (also outside HK). I understand from Geoff that March is not necessarily the best time for a boat trip, but still got a Kittiwake, last year (at sea). Now if everyone else has experience of sea watching and is happy with the routing, may be the society shall give this route more tries.