The cache is not at the posted coordinates. Instead, you'll find Jumar there. Find a plaque about Jumar at the posted coordinates for the final cache location. Use the standard alpha-numeric conversion (e.g., A=1, B=2, C=3, etc.) to answer the below questions. The cache is at N 37 30.ABC W 122 16.DEF. The 6-digit check sum is 31.
A=4th letter of the 1st word in the 2nd line
B=2nd letter of the 2nd word in the 3rd line
C=2nd letter of the 1st word in the 2nd line
D=2nd letter of the 3rd word in the 3rd line
E=1st letter of the 1st word in the 4th line
F=4th letter of the 1st word in the 1st line
A part of the difficulty rating is from the tricky access to the final cache location, but I admit that the hide is rather evil. Be ready to log a couple of DNFs. 
No bushwhacking or wading is required. There's an easy way to get there. The park hour is from sunrise to sunset. Cache on!
Congratulations to Lostfan6 on FTF!