Depth, Draft and Safety Margins on the Bay
Most Chesapeake groundings aren't dramatic — soft mud, a shrug, and reverse gear. But knowing your numbers turns luck into planning.
Know two numbers
Draft: how deep your boat sits. Air draft: how tall it stands, waterline to masthead or hardtop. Enter both in the BayCharts boat profile and your route planner will remind you what to watch.
Charted depth isn't today's depth
Soundings are at MLLW — a conservative low-water figure. Actual depth ≈ charted depth + current tide height, minus whatever the wind has done lately. The Bay's soft bottom is forgiving, but its shoals move; treat single-digit soundings near inlets with respect.
Pick a margin and keep it
A common rule: draft + 2 ft minimum under way, more at speed (boats squat), more in waves, and more where the chart shows a foul or rocky bottom instead of mud. BayCharts flags "watch depths under X ft" on every route based on your profile.
Bridges and wires
Charted bridge clearances are at high water — the safe direction — and appear on the chart like "clr cl 23.1". Compare against your air draft with the tide subtracted only if you must, and never shave an overhead power-line clearance.
Set your boat profile on the chart →