Long story short, not great but not terrible either.
Unlike most Asylum movies, it actually kind of tried a bit. There is an OK plot (slightly cliche for a disaster film however), but other than that it is significantly better than a regular Asylum disaster film (like say, 2012: Supernova).
There are some good quotes and some of the things mentioned are actually scientifically accurate. For example, the size of the Megalodon, and the difference between a squid and an octopus.
Though, of course, the movie itself is unrealistic.
Some scenes are also a bit too fast paced for a movie like this. Some scenes are used over and over again. But they do not seem to be using much (if any) stock footage, which is a good plus.
The CGI is not perfect, but considering what sometimes the Asylum has for CGI, this actually was not horrible.
The acting is pretty good. For an Asylum movie, the acting actually is far greater than average.
Also, spoiler alert but:
The best moment was when an airplane was taken out of the sky by a shark. That was actually entertaining and somewhat epic.
Generally, if you're looking for a not memorable but still somewhat entertaining film, this might work for you, if you are not too much of a judge. I can enjoy almost any kind of movie, so...