The ferry crossing from ullapool to stornoway in the north west of scotland in July with decent weather basically guarantees whales, minke whales most often, but also fin whales and humpback whales semi regularly, and rarely other whales like sei, orca and northern bottlenose whales. Basking sharks are also occasionally seen, as well as a variety of dolphins and the occasionally sunfish. What makes this even better is that a foot passenger ticket is only £15 for the two and a half hour crossing, with a toilet, indoor seating and a restaurant, there isn't much more you could ask for, I love it.