First, let me tell you a story. Back in August 1947 there was a ship wreck in the Strait of Juan de Fuca. It was a foggy night and the cargo ship, 
"Diamond Knot" was rammed by another ship. The Diamond Knot was returning from Alaska with a huge cargo of canned salmon. By the next morning the ship sank and is resting, in 130 feet of water just off shore from Tongue Point at the above coordinates.
Serious recreational SCUBA divers consider this to be the best wreck dive in Washington and Oregon. Ask any serious diver if he's heard of the Diamond Knot. The photo shows the last hours of the ship. More on the ship can be found here
This is all a true story. Now let's embellish it a little to make it interesting to geocachers.......
Captain Onemartini was skipper of the Diamond Knot and he recorded that his ship went down 0.40 miles from the Tongue Point reference monument which is a famous surveying point for the International boundary with Canada. He had a bearing of 127 degrees Magnetic to that shore monument. He used his sextant as a Pelorus and determined this from sightings of fixed points onshore, then plotted the results on his chart.
He claimed he had hidden some of his personal possessions along with his valued gin on the grounds of Camp Hayden. Your first task is to find the monument as its the starting point for your search. It will be a stone pyramid that is close to the shore line with a plaque on the seaward side. This is an easy task with your GPS and the information given so far.
He mentioned that he had come across an old fire hydrant by walking from the monument in a direction of 147 degrees Magnetic for a distance of 0.185 miles. He rested, drank a little more gin and then took off in another direction but his memory was fading a little by this time because of gin poisoning, i.e., he was drunk! He did remember that the number of bolts holding the hydrant to the stand pipe, M was related to his next heading. Finally, after thinking about it he remembered the formula: Magnetic heading in degrees = 6.8 * M. He did remember that the distance to the cache from the hydrant was 688 feet.
Your heading to the cache while standing 40 feet North of the hydrant will be? (This spot was picked to get good GPS readings).
By now you should be getting closer. You're looking for a plastic one pint pill bottle hidden out of direct view. It contains South Pacific coins & odds and ends plus a log.
Captain Onemartini didn't have GPS in those days. In his time, the normal approach was to solve this with compass and pacing off the steps taken. A difficult and inaccurate method in this terrain. A better method is to put your GPS to work if you know how. It will be much much easier. That's where you come in.
Comments: 
- All bearings are Magnetic. If you use TRUE headings, deviation is East 19°.
- Units are statute miles and feet. 1 mile = 5,280 feet.
- GPS coverage will be problematic in spots...you need to work around this and use judgement when needed. This is particularly true in the growing season with leaves on the trees.
- A Compass gives an immediate sense of direction and helps alot.
- This cache is intended to force you to think about using your GPS in different ways and show off the sights of Salt Creek, Camp Hayden and Tongue Point. The operators manual can help you in projecting waypoints.
- Enjoy your visit. This is one of my favorite coastal areas besides Cape Alava.
You'll notice the past military presence here as this was an important coastal defense post at one time.
This is not an easy cache but don't give up. Plenty of chances to make a calculation error. Send me an email for more clues if you need them plus some pictures. The hint has helped alot of people.
This is a good safe family cache that can be enjoyed along with a picnic on a lazy afternoon. Basic High School math required so a calculator is helpful. Have fun!