F5 Robotics has released their XStream ROV thrusters in 3" and 5" versions. There has long been a need for an affordable ROV/UROV thruster for the DIY market. A large number of people choose to build their own underwater vehicles but making a waterproof and effective thruster has always been the hardest part. F5 has changed that with their affordable thruster packages. The 5BL XStream is perfect for large to medium projects and the 3BL XStream is aimed at smaller compact projects.
Even the cheapest thrusters are well over $800 with a speed controller. The F5 Robotics 5BL and 3BL thrusters start at just $199 and have a variety of options including an integrated reversing brushless speed controller that take any RC PWM input making them not only affordable but simple to use.