"Anchoring in Ft. Lauderdale: First and foremost, there is a 24 hour anchoring limit, which means that you can only anchor for 24 hours within city limits. There are two known anchorages in Ft. Lauderdale. The "free" anchorage is at Lake Sylvia, which can be accessed from the ICW (consult for exact location and approach). Lake Sylvia is a large circular basin surrounded by large waterfront homes. No dinghy facilities or places to come ashore are nearby. The nearest places to bring a dinghy or tender to are a few waterfront restaurants near the mouth of the entrance to Lake Sylvia, but they are not free and will expect you to eat or drink there and you can't leave your dinghy there. Lake Sylvia is well protected though, so if the weather is nasty you can drop an anchor there and rest for a while. There is a sandbar in the middle of the entrance to the lake, so you must hug the eastern side of the channel to stay in deep water. Once inside the lake there is more depth.
The city mooring field is on the south end of the Las Olas Bridge and features 10 mooring balls at $20 a night. You can hail the Las Olas Marina on the VHF Channel 16, or call them at 954-828-7200. The moorings are available on a first come, first served basis. If you take a mooring you must dinghy over to the marina to fill out the paperwork. There is a dinghy dock there, as well as comfort facilities. If there is no mooring available when you arrive, you may anchor on the outside of the mooring field overnight but you must pull anchor by noon the next day. The dinghy dock is only available during the business hours of the Las Olas Marina, which are 8 am to 4:45 pm.
If you arrive during bad weather and have to choose between the city mooring field and Lake Sylvia, the latter is much more protected from the elements and traffic from other boats. "
So it looks like that sandbar (charted at 1' at the east end) is part of the reason someone called it shallow, but it certainly sounds legal enough if you don't mind being captive [sic] on the boat. Might be worth the twenty to use the mooring field and be in the middle of everything, unless that 24-hour period is all you need.
The later Travis McGee books mourned the overdevelopment of "Fort Liquoirdale" and I'm afraid old Travis would be rolling in his grave by now, most of the invaders don't even know his name.