Last year we had a very interesting talk on a trip undertaken on, I think, the ferry to the Scilly Isles. 

I spotted these three-day courses which take place on the Portsmouth-Bilbao ferry that might be of interest.  Run by the Biscay Dolphin Research Programme, there are three trips on board the P&O ferry, at a very reasonable cost (to my mind), one in June and two in September.  See this link from the Environmentjob.co.uk website, or go directly to the Marinelife/Biscay Dolphin Research Programme website at www.biscay-dolphin.org.uk.