The squirmer is a canonical model for swimming microorganisms: tangential surface velocity drives locomotion and sets the far-field flow signature.
Lighthill (1952), Blake (1971): squirmer surface velocity v_theta = B1*sin(theta) + B2*sin(theta)cos(theta). B1 sets swimming speed U=2B1/3. beta=B2/B1: pusher (beta<0, like bacteria), puller (beta>0, like algae), neutral (beta=0). Far field: pusher/puller are force dipoles (stresslets).