Looks like Amphidinium on a first glance. The "beak" is what's giving it away.
Note that there are thousands of dinoflagellate species and if this one is actually part of the Amphidinium genera is nearly impossible to tell without DNA analysis.
Hello everyone and welcome to this little microscopy thread! Many hobbyists stumble upon microscopes once they are dealing with a pest they can't properly identify any other way. Besides their obvious usefulness when dealing with a problem, microscopes grant access to a whole new world many...