NInja Squid ain't that great. You can replicate the no-ripple swimming by just slowly moving your stick in squid form, and Ninja squid neither eliminates ripples when climbing walls nor removes the ripple noise. Plus, you can still get tagged by Sensors and Echo. Just run Cold Blooded instead if you want to be sneaky. It may not come into play every match, but you will be very, very glad you have it when you do fight an Echo or an Echo chain (which happens much more at high ranks). This especially true for weapons like the Luna that need to get in close to kill.
For that same reason, swim speed is great on the Luna.