The SeaTac Airport is right by the I-5Take the WA-518 from the airport to I-5 North
Drive 28 miles to exit 182 for I-405 S/ WA-525 N toward Mukilteo
Keep left at the fork and merge onto WA-525 N
Drive 9 miles and the 525 will take you straight to the ferry. See Ferry Etiquette.
Ferries run every half hour, until later at night. Starting at 8:30 or 9, depending on the day, they start running every hour. Check the website:
When you deboard, follow traffic up hill to continue on the 525.