To study corals, scientists typically use a quadrat. which is essentially a simple waterproof frame to place over coral to measure the coral size. That's method is slow, relatively innacurate, expensive as it requires experienced divers, and potentially dangerous as divers would have to dive up and down many times.
With a group of my young students, we set ourselves to create an "upgrade" for the quadrat, by replacing the mecanical device, by an optical one, we called the "Laser Quadrat".
The prototype device performed very well in a controlled environment (coral tank at the SWIMS Institute)...
As well as in an open environment, at sea (Hoi Ha Wan).
We have also attempted mounting the laser quadrat under an autonomous sailing robot in Malaysia (see photos below, credits to Ken Chew, Joe Chew, Eddie Yung):