I wasn't exactly in your shoes but was definitely on the bottom half of the ladder at the boat school. The only thing I think that saved me was maxing out the ASTB and having a good interview. There's still time to make up for grades. No you don't have to be a Trident scholar, but just do the best job in your classes these next three semesters (not four, you select half-way through firstie year). There's still time, and your military performance can help alot too.
It's not going to be all the guys at the top of the OOM ladder that get aviation. They do pick people on the lower end of the ladder (like me) for exceptional performance in other areas (ASTB, interview, and military performance). It matters more than you think. Also, luck can play a role as well. When it came close to graduating, there were quite a few aviation selectees in my class that found out at the last minute that they were not medically qualified, and it opened up a few more slots for people that were next in line. Not only that, but a couple people started taking IFS and decided that it wasn't for them, thereby opening up a couple more slots. So there is still a chance. However, you really need to buckle down academics-wise. I know it sucks, but it's gonna be worth it in the end. Get extra help, talk to your profs, study in the library (you'll get nothing done in the hall, trust me), and always ask about EI in every class, even if you don't need it, it shows you care.
Good luck, any questions feel free to PM me.