From a Boat
A boat is generally the best way to fish bigger bodies of water. It will give you access to places you can't reach from the bank in fresh water and opens up a lot more types of fishing in salt water. A boat is expensive to buy and maintain, but fortunately you've got other options besides buying one.
Fishing from a Boat in Fresh Water
If you buy a boat for fresh water, be sure to get one big enough for the types of water you fish. A canoe can be a good fishing platform for creeks and small ponds but you'll need a much bigger boat for big lakes, particularly the Great Lakes where you need a boat capable of handling very rough water. Don't go overboard in size because a boat that's too big for the waters you fish can create a lot of problems, too.
Many marinas rent boats or you can hire a guide and fish from the guide's boat, although hiring a guide can be expensive. Another possibility is to join a fishing club as a nonboater. Many bass clubs welcome new members even if they don't have much fishing experience. You'll have to pay for gas and oil for the boat but that is a far cheaper than the alternatives.
Posting notes at marinas in your area or on Internet sites is another way to find fishing partners with boats. Many boat owners like to find partners to help share expenses on fishing trips and you can get access to a boat this way. You'll be expected to pay at least half the cost, but if you post that you're willing to pay all expenses, you're more likely to be find someone to fish with.
Be careful finding partners you've never met. Arrange to meet at some public place like a marina and try to visit over a meal to get to know each other a little before going fishing. Talking over the phone helps but it's safer to meet in person in public first.
Saltwater Fishing from a Boat
Owning a boat for saltwater use can be much more expensive than a boat for fresh water because you'll probably need a bigger boat and upkeep is more expensive. Having your own boat, though, is a great way to be able to go fishing any time you want. Consider all options before buying a boat. If you do decide to buy, the cheapest way to get one is to buy a used boat in the fall at the end of fishing season.
A couple of old sayings will give you warning about buying your own boat. One says the happiest two days in a boat owner's life are the day the boat is bought and the day it's sold. Another says a boat is a hole in the water where you dump your money.
There are few boats to rent on salt water because of the dangers but there are many opportunities to charter boats. For about $100 per person you can often join in with four or five other people and charter a boat for a day's fishing for any kind of saltwater fish in the area. That price also includes use of tackle and bait for the day, so it's not as expensive as it sounds.
A cheaper way to fish is to sign up for a party boat (also called a head boat). These are big boats that take out forty or more fishermen for a half or full day of bottom fishing. The cost is usually less than $50 a day but you'll have to either bring your own tackle or rent it for a small additional price. But you can usually catch enough fish on one of these boats to make the cost worthwhile.

