Drop Cam / Tow Cam

Trying to make myself a camera like the ones used as a tow cam ( capture the strike ) or a drop camera to look at the ocean floor. Trying to make one that will survive down to about 50mtrs . Has anyone tried to make one with any luck or has anyone used one like the weaco ones that you can buy in the shops. Would be interested to know what the image quality is like.
I would buy one of these but they are not rated to the depth I want.
Thanks