Well, of course, being one of the steering members of the Squid Works, I've had my share of opportunities to draw sea creatures (albeit not necessarily "monsters"), so I'll try to find as many as I can and post them here:
This one was a part of a comic jam.
This is one that's been used for banners and all sorts of other stuff, including this ringer t-shirt.
Here it is again in color.
This is one I did for a t-shirt.
A gag strip I did for the Tickle Tape back in the day.