I think you've accidentally added a keyframe. You can confirm by moving the boat (with G) and then pressing the right arrow to scroll to a different frame. If the boat snaps back to where it was before you moved it, then it's been keyframed. Applying the location will keep the boat from moving... but it won't solve the problem. If you want to move it again, you'll have to apply the location again, and so on.
If the above reveals a rogue keyframe, open the graph editor and press A to select all, then Delete to delete all the keyframes (assuming you aren't animating anything that you want to keep; otherwise, just delete the keyframes for the boat).
You can delete all the location keyframes for the boat by selecting it and then looking in 3D view > Properties panel (N in the 3D view) > Transform > Location:
If the values are highlighted green, or yellow like in the above screenshot, that means they have a keyframe. (Yellow means there is a keyframe on this frame, green means there is a keyframe on some other frame).
To delete all location keyframes on that object, right click on one of the values and select Clear Keyframes: