More experimentation with my variable ND filter.

Lessons learnt:
(1) One must be extra assiduous about tightening up the tripod with 5 to 20 second exposures;
(2) You WILL get a lot of magenta lens flare if the sun is in front of you, so either don't do that or brush up on your Photoshop skills;
(3) Stuff, notably water, looks better when the sun is shining through it.