IslandCock covered this one well. I don't know much about private areas, but I'm sure if you did some looking, you'd find a few clubs in the area. My sister in law's father used to own about 80 acres near Awendaw that he made into a private club.
Additionally, there are parks (Francis Marion Nat'l Forest) and other areas where hunting is likely permitted and I'm sure you can find more about this with some easy searching.
Again, as IslandCock said, there are a ton of public boat ramps around that have pretty decent parking and usually aren't too crowded. As far as storage for your boat, there's nowhere free that I know of that you'd want to put your boat. You'll need to look into a storage facility. There are plenty of dry-docking options around here, but since you have a trailer, it'd be much cheaper for you to find a storage facility.
The Charleston Battery is the professional team in town: http://charlestonbattery.com/
There are tons of other soccer activities going on around Charleston.
There's also the Charleston Social Club, which has organized sports activities for adults that include bowling, soccer, kickball, softball, and more. If you're looking for something active to do in a new town, the Charleston Social Club is a lot of fun and usually there's a pretty cool crowd at the games, drinking is allowed, etc.
Also, I know this isn't what your post was about, and you may already be aware of this, but if you're buying a home in Berkeley County (or Charleston County) and don't currently have an ownership interest in property in South Carolina, you should look into the Mortgage Tax Credit that is offered by the State of SC for first-time home buyers. You don't have to actually be buying your first home. Where a typical mortgage interest payment can be taken as a tax deduction, this program allows you to take a tax credit
for 30% of your interest. This is a significant difference and should be researched by anyone buying a home in SC.