Can underwater volcanoes be explosive?
I suppose if you are next to them.....
Hmmm. Not really, not in the sense you mean. When you have a low island volcano like Krakatoa and you have millions of tons of water suddenly introduced into contact with hot magma in a collapse, yeah, it's massively explosive.
However, volcanoes of the type of this volcano off Washington (thousands of feet deep, emitting basaltic lavas from a spreading ridge) are never explosive, or even noticeable at the surface to the naked eye.
nope