Hi there. Bit of an amateur but I am an expat living in the Bahamas. May be able to shed some light on this.

The Bahama archipelago is quite treacherous, but theoretically relatively large ships could navigate some parts of it. For instance, the major pirate base was Nassau. I'll be drawing information from The Strongest Man Carries The Day which goes into more detail if you're interested.

Nassau harbor was considered the best option by the English and was reckoned able to accommodate vessels of about 500 tons or less. The depth of the western channel (still the main entrance to Nassau harbor) was 18 feet at low tide and 24 feet at high tide. To compare this to vessels of the day, HMS Bristol (a contemporary warship), built in 1711, was a 4th rate ship of the line of 50 guns, and displaced 700 tons with a draught of 16 feet. Knowing that it could theoretically enter Nassau harbor but would almost be touching the bottom at low tide. HMS Pearl (on of the ships involved in hunting Blackbeard), a 5th rate frigate of 42 guns, displaced 550 tons, so would be on the upper end of what sailors of the day considered safe for Nassau. Blackbeard's ship, the Queen Anne's Revenge, is estimated to have been 200 tons. The other three major harbors in the Bahamas were Harbour Island, Royal Island, and Hockin Island. Harbour Island was the best choice (the British used Dunmore Town on Harbour Island as their seat of colonial government when Nassau was overrun by pirates) and could accomodate vessels of 200 tons. Royal Island's harbor could accommodate vessels of 100 tons, the the island has no source of fresh water. Hockin Island harbor could accomodate vessels of 70 tons. These numbers are based on the 1698 edition of the The English Pilot, a contemporary book that ship's masters of the day would have been familiar with.

Now keep in mind, these are the best harbors available in the Bahamas, out of hundreds of islands and cays. Even Nassau's harbor has treacherous sandbars and sections that are only 4 to 8 feet deep today. Furthermore, while sandbars are plentiful, there are a lot of submerged ridges of fossilized coral and oolitic limestone. A ship can be dislodged from a sandbar, but these rocky outcroppings would (and do) severely damage even modern vessels.

Also, while we often have a stereotypical image of a pirate ship (like Queen Anne's Revenge) a lot of the Bahamian pirates were actually wreckers. They would salvage wrecks or attack larger vessels that had run aground. These presented a significant human hazard to navigation as well.

Hope that helps answer some of your questions.