Designing a Robot Boat 
There are several important things you must consider when building a robot boat. There are weight issues, balance issues, hydrodynamics, waterproofing, the actuator, and sensing problems. There are many different designs you can do, so let’s just go over what hopefully you can apply it to your own project.

Weight 
Weight is important when loading your robot boat with various equipment. It needs motors, batteries, sensors, controllers, it all adds up. If the weight is too much, the boat will sink dangerously low - or at least add a lot of drag to its movement. Fortunately, this is an easy calculation to do. First add up the weight of all components for the entire boat, including the hull. Then estimate the desired length and width of your boat hull.

Here is how I derived the calculation to determine how much your boat will sink under a given weight and hull dimensions:

·         Density*volume = mass

·         Density of water*boat volume under water = boat weight

·         Avg density of the machine*volume of machine = machine weight

·         Sinking depth = machine wt./(density of water*machine length*machine width)

You want the sinking depth of your boat to be as minimal as possible, but yet deep enough the actuators can go into the water. If you are making a robot sub, then you want the sinking depth to equal the height of the sub to obtain neutral buoyancy.

Mechanisms of motion:

Basic mechanisms that can be used for motion of a floating robot are:

·         Paddled wheel

·         Propelled machine using differential or steered turning

·         Hovercraft mechanism

Paddled wheel design:

Hull Design 
The hull of the machine should support the entire weight of the robot and should float simultaneously. So it should be light as well as strong enough so that you achieve both the purposes. The materials that could be used for making such a structure may include:

·         Thermocol

·         Air filled plastic or wooden case

·         Foam core

·         Light wooden base

Mechanism for guiding the ball:

Now this is the place where your creativity will creep in. There can be several options, you need to think of the most efficient available.

·         Guiding the ball using a guider.

·         Clamping and throwing.

·         Lifting and dropping.

The questions that you might need to answer here are:

·         How will the mechanism overcome the water drag?

·         How will it put in the maximum no. of balls in the given time?

·         How can it be controlled in the simplest way?

And a few more…

Control and Electronics:

The competition being manual, The machine has to be controlled by a remote controlled which can be wired too. The motors driving the paddle propellers, etc. can be controlled using switches (dp-dt switches). Moreover the motor, if applicable, controlling the ball guiding mechanism in the machine will also require a similar control.