Ive also droped john boat trailers off banks and ramps with drop offs. Ramps usally go smooth if you go real slow it will just bump agaist the bottom of the frame as the tire rolls off the drop off.
If your in a 2 wheel drive you might try leaving the boat tied to the trailer in back .It will float the trailer. And try pulling it back out first.
We used to lauch off a river bank when i was a kid and ive seen servral 2 wheel drive 70s fords of my granffathers pull the trailer back from clean outa of sight. On river mud. No way id try that my self however.