The imagination is the only limit to what you can build with LEGOs. One of the more impressive constructions you can create is a boat that actually floats for extended periods on water. While LEGOs tightly fit together, they do not create a waterproof seal. Water eventually floods into the vessel, catastrophically overwhelming its buoyancy, leading to a watery grave for most LEGO boats. The key to keeping your boat afloat is to trap air in the blocks just below the water surface, thereby keeping the boat floating high enough to avoid leakage. If the boat is too heavy and overwhelms the upward force of the air, the downward force of gravity will be enough to sink your creation.
Cover the bottom of the 6-by-10 panel with bricks. Add some bricks with upward-slanting sides toward the front end of the panel to give the boat that classic look.
Add some railings, a motor and a slanted nose to the boat. There isn't any specific method for decorating the surface of your flat panel, but try not to make any part of your boat taller than three or four bricks. Remember, you're trying to keep the weight of the vehicle low enough to allow buoyancy to keep things floating.
Add the windshield, steering wheel, chair and LEGO figure. Ensure that the boat is symmetrical so it won't tilt to one side. A tilting boat will cause air to escape the lower blocks, lowering the structure's buoyancy.
Hold your boat over the water and slowly lower it. If you see the boat leaning forward or backward, pull the boat out of the water and even out the weight by adding or subtracting a few pieces.
Allow the balanced boat to float in the water. Watch for any bubbles. If the boat is completely balanced, the air will remain in the lower blocks and the boat will not sink.
For extra security, cover the bottom of the boat with a few strips of duct tape. The tape will eventually get wet and lose its grip, but it will ensure the air within the bottom bricks doesn't escape. Float your boat a sink or bathtub where the water is relatively motionless.
Don't add too many bricks to the upper portion of your boat. While helicopter pads, swimming pools and four-tiered windshields look snazzy, they will weight your boat down and cause it to sink.