Hi @Mary-Claire, congratulations on completing your ROV build!
If this is in manual mode, that sounds likely to be a motor configuration issue - either due to one or more thrusters with reversed directions, or connected to the wrong input. I’d suggest you use the QGroundControl Motors Setup Page to confirm that each control slider corresponds to the correct thruster in the frame, and once that’s confirmed you can run the automatic motor direction detection to fix the control for any of the thrusters that have their coils reversed.
It’s also worth checking that all the thrusters are oriented correctly, have the expected clockwise or counter-clockwise propeller, and can be spun freely by hand while off (ie don’t have anything stuck in them).
I’m assuming this is due to the same issue as above, but it could also conceivably be due to an uncalibrated or faulty sensor. It may be worth using the Sensors Setup Page to calibrate the sensors