Do I need ESC's ?

[ChaseNoble]

I have 4 of these http://www.ebay.com/itm/230438229146?ss ... 1438.l2649 . I have them 2 of them for depth, 2 for left/right-straight. So do I need ESC's and how many do I need?

[KR2_Diving]

Looks like they are brushed motors, so you could get away with not using ESCs. Have you requested the data sheet from the guy?

[scubersteve]

The only reason you might want ESCs is for proportional control if you want to maintain something other than top speed without manually switching them on and off.
Of course the same thing might be accomplished with potentiometers...