Is it possible to catch squid without a fishfinder?

I fish off of a SUP and have landed huge lingcod, etc and easy limits of Dungeness from it but I mostly know where to fish from using Navionics on my phone or visual cues on the surface (kelp).

Have still not figured out a FF setup for the SUP but interested in squid. Is it possible to find them (like if they're always next to a buoy or something) without a FF or is it pretty much necessary? I have no issues paddling far out on the SUP.

Sure it's possible!  But it sure helps to have a fish finder.  Or, other kayakers near by with them 

I brought one of these: https://deepersonar.com/en-us/products/deeper-sonar-pro for use with the SUP (for the occasional camping trip that ends up near a lake)

As long as you can clip it to your board (via short rope), and waterproof phone case. Works pretty well.