We rode the submarines last week. They were a lot of fun. The ride lasts about 12 minutes or so, which is nice. The line lasts about 4 hours, without shade. That’s not so nice.
Luckily we were admitted an hour early per Disney’s policy of letting hotel guests in prior to opening (3-4 days a week). Thanks to that I was able to stand in a huge line with every other hotel guests outside the park gates and then walk briskly to the subs to stake my claim while my family strolled aimlessly down Main Street.
Due to my mad speed-walking skills we only had to stand in the actual submarine queue a little over an hour. It was worth it.
The ride is what you want it to be. Get there fast, and get there early.