Be there early to get a window seat if you go whale watching. You can rent binoculars for 5 dollars and keep them during the trip (trust me, it is worth it). No cash accepted.
Some boats have stabilizers, some don't. Ask ahead of time. Buy seasick meds for $.25 and take them at the start - the last hour outside Victoria can be rough!
Clipper Vacations operates year round ferry service between Seattle and Victoria, BC plus a seasonal Seattle to San Juan Island ferry and whale watching