I noticed a green-colored marine arthropod in harbor in the US San Juan Islands (early July 2022, around noon), specifically Haro Strait, and took several pictures from the dock.
The bug was approximately 1 centimeter in length. I am guessing that it is algivorous (or algivore-vorous) based on the green color. It was in constant motion in sunlight, possibly hunting though it wasn't clear what it was going after (though the area was very algae-rich).
Apologies for the low quality images, some of these are stills from a movie (I had issues focusing because it was underwater and it was swimming around quite quickly).
Google image search was not very helpful, and neither was iNaturalist.