How deep is Keystone Jetty (Fort Casey Underwater Park)?

Keystone Jetty (Fort Casey Underwater Park) ranges from 3 to 18.3 metres deep (10–60 feet). It is a saltwater site rated as intermediate difficulty. Depths vary across the site, so plan your profile to your training and verify conditions locally.

Is Keystone Jetty (Fort Casey Underwater Park) a shore dive or a boat dive?

Keystone Jetty (Fort Casey Underwater Park) is a shore dive — you can enter from land. The entry is recorded as an easy walk-in. The site is recorded as tide-dependent (slack tide only), so check local tide tables when planning your entry. The entry area is recorded as moderately exposed to surge. Basic facilities are recorded at or near the site, and cell service is recorded as good. Entry details and parking notes, where known, are listed in the access section of this page.

Can beginners dive Keystone Jetty (Fort Casey Underwater Park)?

Keystone Jetty (Fort Casey Underwater Park) is rated as intermediate difficulty, which may not suit new divers. Listed depths run from 3 to 18.3 metres (10–60 feet). Access is from shore, with the entry recorded as an easy walk-in. Consider your experience level, conditions, and local guidance before planning.

What will I see at Keystone Jetty (Fort Casey Underwater Park)?

Divers at Keystone Jetty (Fort Casey Underwater Park) in United States commonly report sightings of Bull kelp, Nudibranch, Rockfish, Plumose anemone, and Giant Pacific octopus. Nudibranch, Rockfish, Plumose anemone, and Giant Pacific octopus are recorded as common sightings, while Bull kelp is seasonal. Marine life varies by season and conditions—check the site page for recent diver observations and photos.

Map of Keystone Jetty (Fort Casey Underwater Park)

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IntermediateShore entry

Keystone Jetty (Fort Casey Underwater Park)

Washington, United StatesDirections

Open Water suggested3–18 m (10–60 ft) depthShore entry7mm or semi-dry + hood typical

Keystone Jetty (Fort Casey Underwater Park) at a glance

Keystone Jetty (Fort Casey Underwater Park) is an intermediate shore dive site in Washington, United States with depths of 3–18.3 m (10–60 ft). Typically most favorable Jul · from 3 years of archive data. Divers commonly see Bull kelp, Nudibranch, and Rockfish. Recent reports put the water around 12°C (53°F). Check the latest conditions and entry details before you go.

Favorable window now· until 19:00 · sunset 18:01

Forecast for this hour · 13:00 · run 15 h ago

0.0 m (0.1 ft)waves — under half a meter expected (waves — under a foot expected)

Tap a factor for its source and model point · Forecast 12°C · seasonal avg 11°C ( · Forecast 53°F · seasonal avg 53°F)

Site hazards: Strong Admiralty Inlet currents outside slack, active ferry traffic on the far side of the jetty, bull kelp entanglement in season, exposed conditions in wind

Read the full hazards ↓

Dive windows this week

Mon

0.0 m waves · 4 kn wind (0.1 ft waves · 4 kn wind)

Tue

0.0 m waves · 5 kn wind (0.1 ft waves · 5 kn wind)

Wed

0.1 m waves · 3 kn wind (0.4 ft waves · 3 kn wind)

Thu

0.4 m waves · 6 kn wind (1.2 ft waves · 6 kn wind)

Fri

0.2 m waves · 5 kn wind (0.5 ft waves · 5 kn wind)

Sat

0.0 m waves · 3 kn wind (0.1 ft waves · 3 kn wind)

Sun

Favorable windowModerate window— no window

Every forecast dive window each day, site-local time, from wave and wind forecasts. Numbers under each bar are daylight averages.

First light 7:15 · Sunrise 7:47 · Sunset 18:01 · some windows run past sunset

Source: Open-Meteo marine · model point 6.0 km from site · updated 25 Oct, 22:25 GMT-7

Forecast only — always assess conditions on site.

Compare this weekend’s windows near Keystone Jetty (Fort Casey Underwater Park)

Forecast · NOAA tide model

Tide & slack timing

Recent diver reports

Dated firsthand observations from divers — not current conditions.

No diver reports for this site yet. — one dated observation helps every diver after you.

Dived here today — did the forecast match?

What Divers Say

Known for: Nudibranch, Rockfish, Plumose anemone

Best time: Slack water on small exchanges; summer has kelp and the most fish, winter the best visibility

Based on community reviews and site data. Conditions vary — always verify before diving.

Best months, historically

What conditions have historically been typical at this site, month by month — not a forecast.

January, 95% of days have historically been favorable, water has typically been 8°C (47°F), waves have typically been 0.2 m (0.7 ft), wind has typically been 12 knots
February, 80% of days have historically been favorable, water has typically been 8°C (46°F), waves have typically been 0.3 m (0.9 ft), wind has typically been 14 knots
March, 88% of days have historically been favorable, water has typically been 8°C (47°F), waves have typically been 0.3 m (0.9 ft), wind has typically been 13 knots
April, 91% of days have historically been favorable, water has typically been 9°C (49°F), waves have typically been 0.3 m (0.9 ft), wind has typically been 14 knots
May, 99% of days have historically been favorable, water has typically been 11°C (51°F), waves have typically been 0.2 m (0.6 ft), wind has typically been 12 knots
June, 98% of days have historically been favorable, water has typically been 12°C (54°F), waves have typically been 0.2 m (0.6 ft), wind has typically been 11 knots
July, 100% of days have historically been favorable, water has typically been 14°C (57°F), waves have typically been 0.2 m (0.5 ft), wind has typically been 11 knots, historically most favorable
August, 99% of days have historically been favorable, water has typically been 14°C (58°F), waves have typically been 0.2 m (0.5 ft), wind has typically been 11 knots
September, 99% of days have historically been favorable, water has typically been 13°C (56°F), waves have typically been 0.1 m (0.5 ft), wind has typically been 10 knots
October, 92% of days have historically been favorable, water has typically been 11°C (53°F), waves have typically been 0.2 m (0.8 ft), wind has typically been 13 knots
November, 81% of days have historically been favorable, water has typically been 10°C (51°F), waves have typically been 0.3 m (0.9 ft), wind has typically been 13 knots
December, 78% of days have historically been favorable, water has typically been 10°C (49°F), waves have typically been 0.3 m (1.0 ft), wind has typically been 15 knots

July has typically had the largest share of favorable days here. Conditions vary year to year — this is historical context, not a forecast.

Based on 3 years of archive data. Bar height shows the share of days each month whose conditions have historically scored favorably.

Marine life seen at this site

Species noted at this site — not a promise of what you’ll encounter.

Species seen here

Rough labels: “Commonly seen” usually means two or more recorded sightings near this site in public dive logs (GBIF), “Occasionally seen” one; “Seasonal” and “Rarely seen” come from dive-guide research. Not a measured rate.

Fills & rentals nearby

No dive shops mapped within 25 km (16 mi). Know one? Add it to the map.

Data updated June 2026

Site details

Washington's other underwater state park, along the rock jetty protecting Keystone Harbor at Fort Casey State Park on Whidbey Island, next to the Coupeville-Port Townsend ferry landing. The jetty boulders are plastered with anemones and nudibranchs and shelter wolf eels, octopus and big lingcod, with about 55-60 ft of depth at the jetty tip. Admiralty Inlet currents sweep the site hard, so it is strictly a slack-water dive planned with Admiralty Head current predictions, and divers must never round the jetty into the active ferry lane.

reefshorewall

Strong Admiralty Inlet currents outside slack, active ferry traffic on the far side of the jetty, bull kelp entanglement in season, exposed conditions in wind

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