Hi! I'm in my first year on the Marine and Natural History Course (started in September 2015). The field trips that I have been on so far have all been free and were part of the course. However, there are some trips coming up for me in February + March 2016 that cost like £20/£30 each. The trips were optional though, however they are certainly worth the money that you pay for them. You can rent out camera equipment from the photography store for free. The store is amazing; it has such a range of camera's and lenses etc and the fact that you don't have to pay to borrow anything is great!
Just to let you know, I went with Padi for my diving course and I had to be an advanced open water diver before I started in september this year (however, others did their diving courses here in Falmouth after they started the course). The earlier you can do the courses the better it will be, but for me they didn't take that long to do.
I think I made the best decision coming to Falmouth; It was the only I wanted to go to from the start. For me there are no downsides, accommodation is great, you have a shop on campus and there's a free asda bus for you to go and get your shopping. The bus to falmouth from the penryn campus takes about 10/15 minutes and is really cheap (with your student ID it's £1 for a single bus ticket). There are more shops in Falmouth than I was expecting, also the local beaches like Gylly beach and Swanpool beach are nice. The only problem I would say for me is getting back home and then back to Falmouth again, it's a bit of a long ride by train or by coach but it's worth it!
Sorry for writing quite a bit, I just wanted to answer some of your questions, hopefully, and give you a sense of what it's like here at Falmouth. I was nervous when applying whether I made the right decision but I wouldn't wish to be anywhere else studying anything else. Once again the course is fantastic and Falmouth is equally great. I hope you decide to come here. I would be more than happy to answer any more questions if you have them, that applies to anyone else on The Student Room.