An oddity this - the premise is good but the movie lacks the financial resources to deliver in the setpieces. It's a pity as the movie moves at a fair pace for it's 85 minutes and the characters are mostly likeable, with reasonably decent acting all around. It's just the sets and CGI that really let the film down. The interiors of the several submarines and ships just look under detailed, poorly lit and not at all convincing. As for the titular monsters, well they don't really have all that much on screen time. Certainly, the giant shark has the lions share of the big setpieces and on screen time but is also the least convincing. The giant octopus is more of a support but looks much, much better animated to my eyes - hence it's lesser appearances. There is also a lot of repetition in the shots of the shark that just remind you of how average the CG is. Granted though both monsters are absoluteley gigantic in size, and at least the CG improved for the (brief) scenes of the two in combat. This film reminded me of Shark Attack 3 (which featured a Megalodon) and Octopus but with poorer CG than those two movies. The scene where the shark takes the passenger plane down is appalling with this really awlful blurry style CG and it only improves slightly where it takes a huge bite out of the Golden Gate Bridge in a promising scene that ends only too quickly. There is much talk of a city in chaos and a death toll in the thousands but nothing is really seen on screen! I didn't quite buy the romance between the two scientists but the team of 3 boffins who often find themselves at odds with the industro-military complex were actually quite engaging. It must also be said that the DVD picture was razor sharp and the movie did actually have some decent cinematography as well - particularly with some really nice opening footage of glaciers and sea life and some rather impressive sunsets/sunrises too. It is just the variable FX work that lets the film down together with the brevity in the attack scenes; an example is an attack on an off shore platform that is only too brief - although I did enjoy the actually rather chilling image of the octopus' eye during the assault. In fact, if you look at the trailer on YouTube, then in all honesty, you will see the very best of the monster setpieces - just like Television X after 12pm, the movie doesn't offer that much more! Oh, and as for the extras, the making of is rubbish - mostly Lorenzo Lamas (who only has a small role) talking a lot of BS. There is absoluteley nothing at all on the beasts or the FX work.
All in all, it is watchable but stick with 20000 Leagues Under The Sea or It Came From Beneath The Sea for the definitive giant cephalopods and Jaws or Deep Blue Sea for the finned menace favourites!
If you can find it, I would actually recommend Nu-Image's Octopus - similiar but much better CG and some really good scenes of the eight legged beastie devouring people & ships, submarines etc.