This is a very small light sensor. A photo resistor (also known as a photodector, or photocell) changes resistance depending on the amount of light it is exposed to.
Ultrasonic Module HC-SR04 Distance Measuring Transducer Sensor.
This is the waterproof inspection LT2 Robot. It has flipper arms to help it climb obstacles and for better maneuverability. It is capable of wireless or tethered control. The tethered option includes a fiber-optic cable spool up to 1km long.