Olympia, at the south end of Puget Sound, has a maximum tidal range of about 17 feet. Port Townsend, at the north entrance, has roughly 10. The 7-foot difference is not small — it is the result of the Sound being a closed basin into which the tidal wave reflects and amplifies as it propagates south. The southern end’s larger range and the northern end’s stronger currents are the same physics seen from different ends of the same body of water.
This is the Puget Sound–specific working guide to tides — what the named stations actually do, where the strong currents are, and the practical rules a cruiser uses. The comprehensive treatment of tides and currents in the broader Salish Sea is in the education piece on Tides and Currents in the Pacific Northwest; this is the blog companion focused on the Sound itself.
Mixed semi-diurnal — quickly
Puget Sound has mixed semi-diurnal tides: two high waters and two low waters per day, with the two highs and the two lows of unequal height. The forecasted Higher High Water (HHW) and Lower Low Water (LLW) are usually six to seven hours apart and produce most of the day’s tidal range. The Lower High Water and Higher Low Water sit between them and are smaller.
The practical consequence: which low tide matters for your anchorage. A spot with 8 feet at the LHW may have 4 feet at the LLW. The chart does not tell you which one you have on a given afternoon. The tide table does.
Stations and ranges
NOAA publishes tide predictions for stations throughout the Sound. The reference station is Seattle (NOAA station 9447130). Approximate ranges, MLLW datum, on a spring tide:
| Station | Range |
|---|---|
| Port Townsend (north entrance) | ≈ 10 ft |
| Seattle (Elliott Bay) | ≈ 13 ft |
| Tacoma (Commencement Bay) | ≈ 15 ft |
| Olympia (south end) | ≈ 17 ft |
The amplification southward is the closed-basin effect: the tidal wave entering the Sound at Port Townsend reflects off the south end and constructively interferes with the next incoming wave. The southern stations get larger ranges and longer slack-water windows than the north — the wave is broader and slower at the reflection.
For practical anchoring, planning, and shoal-water navigation, use the prediction for the station closest to your specific position, not for Seattle. A 17-foot tide in Olympia behaves differently from a 13-foot tide in Seattle, and the difference matters.
Currents — different stations, different physics
Puget Sound tide tables tell you height. They do not tell you about current. For currents you need NOAA’s separate Tidal Current Predictions (or, for cross-Sound passages and Canadian waters, the Canadian Hydrographic Service’s Current Atlas).
The Sound’s named current chokepoints, with peak flows on a spring tide:
- Admiralty Inlet (north entrance, between Point Wilson and Whidbey) — 3–4 knots peak ebb. The gateway from the Strait of Juan de Fuca to the Sound; a head-current condition for inbound traffic on a strong ebb.
- The Tacoma Narrows — 5 knots peak. The constriction between Tacoma and the Kitsap Peninsula. Manageable under power; a slog under sail against the current.
- Deception Pass (north Whidbey, technically out of the Sound proper) — 8–9 knots peak. Slack window: about 15 minutes. Recreational boats transit only at slack.
- Rich Passage (between Bainbridge Island and Manchester) — 3 knots peak. Used by Bremerton-bound Washington State Ferries; commercial traffic monitoring on Channel 13.
- Agate Passage (between Bainbridge and Suquamish) — 4 knots peak. The shorter route from Eagle Harbor north to Liberty Bay.
The general rule: maximum current occurs midway between high and low water (mid-tide), not at the extremes. Slack water — the moment of zero current — lags the tidal extreme by one to three hours depending on the geometry of the passage.
This is the most-skipped fact in Puget Sound passage planning. Slack water is not high tide. If you plan a Deception Pass transit using the Seattle tide table, you will arrive at the pass in a four-knot current. Use the current prediction for the pass itself.
Working rules
Plan strong-current passages at slack. Slack windows in the Sound’s chokepoints range from 15 minutes (Deception Pass) to 45 minutes (Tacoma Narrows). Build the schedule around the slack window, not around your departure preference.
Add current to your boat-speed math. A 35-foot cruising boat motoring at 6 knots through the water makes 8 knots over ground with a 2-knot favourable current and 4 knots over ground against the same current. Over a 25-mile passage that is the difference between a four-hour day and a six-and-a-half-hour day. Adjust departure time accordingly.
Use NOAA, not the chartplotter app. Many navigation apps display current arrows; the underlying data is often interpolated and simplified. For critical passages — Deception Pass, the Narrows, Admiralty Inlet — check the official NOAA prediction for the named reference station. The chartplotter is for situational awareness; the prediction is for planning.
Negative tides expose hazards. A −2-foot tide in South Puget Sound exposes rocks, shoals, and mudflats that are safely covered at MLLW. On a minus-tide morning, slow down, read the chart with extra care, and run the GPS track well clear of charted shallow areas. The boat that goes aground on a charted shoal at LLW is the boat that planned by the average and not the extreme.
Wind against current. A 15-knot southerly opposing a 3-knot ebb in Rosario Strait or Admiralty Inlet produces 4-foot short-period chop within an hour. Always check the current direction relative to the wind direction for the passage time. The same 15 knots is a different sea state depending on the relationship.
A passage example
Plan: depart Friday Harbor (San Juan Island) at first light, head south through Cattle Pass, into Rosario Strait, around Whidbey Island via Deception Pass, into Skagit Bay, and on to Anacortes. Total roughly 45 nm.
The decisions:
- Cattle Pass slack at 0612 (NOAA prediction). Be there at 0600.
- Deception Pass slack at 0834 (separate NOAA prediction — different station from Cattle Pass). Distance Cattle to Deception ~16 nm; cruising speed 5.5 knots in current = arrival around 0900. Late by 26 minutes. Adjust: leave Friday Harbor 30 minutes earlier, arrive Cattle 0530, transit slack ±30, then push for Deception arriving 0830. Workable.
- Rosario Strait — check the wind direction against the current. Forecast is south at 12 knots, current ebbing south to north until 0900. Wind with current; comfortable.
- After Deception, Skagit Bay is shallow and full of charted shoals. Tide is rising past LHW around 1100; safely above the −1.2-foot LLW that strands boats off Goat Island.
The plan works. The same passage one tide cycle later (Cattle Pass slack at 1840) would put you at Deception Pass after dark in late October — a different decision.
This is what tide and current planning looks like in practice. It is not optional. It is the discipline that turns a 45-mile day from a hard slog into an unremarkable cruise.
For the deeper treatment — mixed semi-diurnal physics, the Rule of Twelfths, Salish Sea–wide chokepoints (Yuculta Rapids, Seymour Narrows, Active Pass), and the planning sequence in detail — see Tides and Currents in the Pacific Northwest in the education library.
Slack water is not high tide. The chart is not the tide table. The tide table is not the current prediction. All three matter on a Puget Sound day.
The boat that misses the slack is the boat that learns the difference, in the worst possible classroom.