When backing a boat trailer into the water, consider the following aspects:
Practice your backing skills in an empty parking lot before attempting at the boat ramp.
Use your vehicle's side mirrors to monitor the trailer's position.
Keep your boat's bow line secured to the dock while backing the trailer.
Don't submerge the entire trailer; only submerge about one-third for a bunk trailer or two-thirds for a roller trailer.
Keep an eye on other boaters and be courteous by waiting for your turn to launch or retrieve.
By keeping these points in mind, you'll be able to safely and efficiently back your boat trailer into the water and load your boat with ease.