Okeechobee is its own kind of day. The chart polygon for it measures 1,372.3 square kilometers, 339,102 acres, close to eight times the size of the next largest water the pack carries, which is Lake George at 175.4 square kilometers. Out in the middle of something that wide the far shore stops working as a reference and you are running on a course and a chart. Most days are not that day. Most days are Lake Istokpoga at 96.3 square kilometers, or Lake Tohopekaliga at 75.1, or a county ramp on water with no name on it at all, where the whole question is which way the channel runs out of the cove and how much you have over the flat before it.
The pack draws 13,643 charted water bodies. Of those, 3,160 carry a name, and 347 named lakes are larger than a square kilometer. Every outline comes from the National Hydrography Dataset, so a cove has its actual edge rather than a rounded-off blue shape, and the depth inside comes from state elevation surveys rather than from a nautical chart, because nobody draws a nautical chart for a lake two counties inland.
Of the 48 state packs, this one ranks fourth by charted water bodies at 13,643. It ranks sixth by named water at 3,160, and fifth by named lakes larger than a square kilometer at 347. Those three rankings together describe a state pack that is heavy at both ends.
At the top end it carries a single body of water of 1,372.3 square kilometers. At the other end it carries thousands you could run around in an afternoon in a jon boat, which is where the gap between 13,643 and 3,160 comes from. Most of the water in this pack has no name recorded for it. It is still drawn, still has an edge, and is still on the screen at a ramp with no bars on the phone.
The count is useful for one practical reason. If you fish small water, the thing that decides whether a chart app is worth carrying is not whether it has Okeechobee. It is whether the twelve acre pond behind the orange grove is a shape on the screen or an empty space between two roads.
| Lake | Charted surface area |
|---|---|
| Lake Okeechobee | 1,372 km² (339,102 acres) |
| Lake George | 175 km² (43,342 acres) |
| Lake Kissimmee | 127 km² (31,308 acres) |
| Lake Apopka | 125 km² (30,888 acres) |
| Mud Bay | 125 km² (30,789 acres) |
| Lake Istokpoga | 96 km² (23,796 acres) |
| Lake Tohopekaliga | 75 km² (18,558 acres) |
| Lake Harris | 74 km² (18,360 acres) |
| Crescent Lake | 69 km² (17,100 acres) |
| East Lake Tohopekaliga | 47 km² (11,713 acres) |
| Lake Seminole | 42 km² (10,453 acres) |
| Lake Griffin | 38 km² (9,439 acres) |
The twelve largest named lakes the Florida pack carries, by charted surface area, measured from the chart polygon itself. The pack carries 13,643 charted water bodies in all, 3,160 of them named, and 347 named lakes larger than one square kilometer.
There is no NOAA chart for a reservoir. The nautical charts cover the coast, the intracoastal and the navigable rivers, and the survey work behind them was never done on a lake sitting inland. Helm builds inland depth from state elevation surveys instead, and pairs it with water body outlines from the National Hydrography Dataset.
That pairing is the whole reason a lake in Helm is charted water. The outline gives the cove and the point their real shape. The elevation survey puts a number under it. Together they are what lets the chart shade water your hull cannot cross and lets a route be planned across a lake against your own draft instead of drawn straight over it and hoped through. How the shading and the router use that number is the same on every water and is written up elsewhere on this site.
The date attached to a lake survey matters more on inland water than people expect, and Helm carries it with the reading. A bottom contour surveyed some years ago is still the bottom. What has changed since is silt in the creek arms and whatever a storm moved, which is worth knowing before you trust a two foot margin at speed.
A contour on a lake is the shape of the bottom. The surface above it is a separate question, and on water held behind a dam that question was answered by somebody in an office this month. Pull the lake down a foot and the bottom has not moved anywhere. The distance between it and your keel has.
So read the contour for shape first. The creek channel running out of a cove is the thing to find, because it is in the same place at any level, and the shoulders on either side of it are what come up to meet you when the water is being held low. A ramp that is fine at full pool can have you idling a long way out with the level down, and the contour is what tells you which direction to idle.
The lakes that are not impounded move too, just on rain rather than on a schedule. Either way the practice is the same. Know the shape from the chart, know what the level is doing on the day you launch, and put the two together at the ramp rather than out at the far end of the lake.
Lake Okeechobee is the largest named lake the pack carries, at 1,372.3 square kilometers or 339,102 acres. Add the next nineteen largest named lakes in the pack together and they come to 1,245.6 square kilometers, still short of it.
Below Okeechobee the sizes tighten fast. Lake George is 175.4 square kilometers, 43,342 acres. Then Lake Kissimmee at 126.7 and Lake Apopka at 125.0, close enough that somebody who runs both would not call either one the bigger lake. Four tenths of a square kilometer under Apopka is Mud Bay at 124.6, which is a fair reminder that the names arrive from the hydrography dataset as they were recorded, and not everything at that size has the word lake in it.
Two of the twenty come out identical. Lake Worth and Blackjack Lake both measure 29.6 square kilometers, 7,314 acres, with Orange Lake two tenths behind at 29.4. Higher up the list, Lake Tohopekaliga at 75.1 is a little over half again the size of East Lake Tohopekaliga at 47.4, and Lake Harris at 74.3 sits within a square kilometer of the larger of that pair. Lake Istokpoga at 96.3 is bigger than any of them.
One thing worth knowing about how the packs are cut. They are cut to a box rather than to a state line, so a lake near the Georgia or Alabama boundary sits in this pack and in the neighboring pack as well. That is on purpose. Working out which side of a survey line your water falls on is not a thing you should have to do before you can download a chart.
Inland lake depth comes from state elevation surveys rather than from nautical charts, and a reservoir sits at whatever level it is being held at that week. Treat the shape and the depth as a guide, keep a lookout, and verify locally.
Depth data. The pack carries Okeechobee as charted water of 1,372.3 square kilometers, 339,102 acres, with the outline from the National Hydrography Dataset and the depth under it built from state elevation surveys rather than from a NOAA chart. That means contours and a depth reading on the water itself, shaded against the draft you entered, and it works on the device with no signal once the pack is downloaded.
It draws 13,643 charted water bodies, which is fourth among the 48 state packs. Of those, 3,160 carry a name, sixth of the 48, and 347 named lakes are larger than a square kilometer, fifth of the 48. The rest are the small ponds and backwaters, drawn from the same hydrography outlines as the big water.
Both of them, in most cases. The packs are cut to a box rather than to the state line, so water near the boundary appears in this pack and in the neighboring state pack as well. Lake Seminole, at 42.3 square kilometers in this pack, is the sort of water that can show up in more than one. Download the pack covering the water you actually run and the line stops being your problem.
Helm Boating