I am new to the ROV community.
I am struggling to select a motor to use for my DIY ROV.
The products I’ve considered are these:
FLASH HOBBY D4215 amazon
FLASH HOBBY D2830 (Can’t paste the link)
I don’t know if this is the right place to ask and this question has probably been answered a lot of times before. Nevertheless, thanks for reading. 
Hi @meo209 , welcome to the forums!
We’re a bit biased, but we would recommend the T200 or M200 for your ROV applications. While you can use regular brushless DC motors in water, after just a few uses the steel bearings are likely to corrode and seize, limiting your vehicles lifetime! The motors Blue Robotics sells also include the WetLink penetrator for reliably bringing the cable into your housing in a way that doesn’t leak - we’ve learned the hard way not to rely on potted penetrators!
I’ve seen these, although they are just too expensive.
Sorry about that @meo209 -
You do get what you pay for in life, and the ocean can be a very unforgiving environment for technology that isn’t rated for it. We do strive to be as affordable as possible, as well as transparent! We hope to launch a smaller version of our motors and thrusters someday that would be a bit cheaper…
Hopefully you will succeed in that goal!