Although the name implies you're going to catch monsters, Monster! Bass Fishing is a normal fishing game where you can catch a variety of fish including various bass, northern pike, catfish, and more. The "monster" part is that you get bonus points for catching monster-sized fish.
The game is played in one of two modes, Challenge or Free Fish. In Free Fish, you can fish in any location that is unlocked for as long as you like. In Challenge, you are competing in a tournament and will have a time limit and a specific location to fish at.
When you start at a location in either mode, you have the option to move your boat to any place on the map. However, this does take time and may not always be in your best interest in the Challenge mode. You can then either start casting, or you can change your lure first.
Catching fish is really just a matter of using a good lure and tempting movements. When a fish strikes, you need to keep enough pressure on the line to keep the hook set, or the fish will get away. If you let the line get too tight, the line will break and you'll lose the fish then as well. Now just reel it in and see what you caught.
The GUI shows a nice fish finder that is color-coded by the type of fish that is seen. Note that this finder is not always accurate.
Statistics for the game are very nice. You can see a nice picture of your fish that you catch along with the size of it. The top 6 can then be saved in the Aquarium for viewing at any time. Your tournament scores will be based on weight of fish and any monster bonuses (bonuses for catching one of the top 3 largest fish that round). Winning the tournaments will unlock new locations and let you progress to a new location for the next tournament. It will also get you a nice trophy.