We did the trip to Staffa/Fingal's Cave and the Treshnish Islands. Dead easy to organise - bought tickets in the tour office at the Calmac terminal on the pier at Oban. The first bit of it was rather dull - waiting for the ferry, sitting on the ferry across to Mull (Craignure). Then we got on a minibus across Mull to Fionnphort - the "ferry terminal" to Ulva, or just a collection of sheds and a car park as far as I could see. The latter half of this trip was along a very narrow single-track road with some quite scary twists and turns along the edge of some steepish drops: but clearly the driver had done it before, so no real drama.
The boat itself was a fishing boat with an open rear deck and a cabin at front. The weather was initially overcast but warm, so we sat at the back; later the sun came out and it was very pleasant, the sea flat calm all day.
En route to Staffa, we saw seal cubs basking and and a basking shark - indeed, during the day we saw 3 basking sharks, or possibly the same one stooging around in 3 different places. Staffa is brilliant, a volcanic isle of basalt columns like the Giant's Causeway in N Ireland: there are various clusters around the island like the Causeway (but smaller). Fingal's Cave - a hollowed-out hole in the the cluster of columns, with the columns you stand on mirrored above your head - is surely one of the natural wonders of the world. We had an hour ashore there, and there are lines and steps to allow you to get along to the Cave and to get to the top of the island and explore (briefly) the rest of it. Watch your step, though, normal elf''n'safety rules don't apply - a German tourist fell off and killed himself recently
Then back in the boat and on to and around the Treshnish Isles - a collection of mostly low-slung rocks with loads of birds. We landed for an hour on Lunga, one of the largest. Personally I would not know a guillemot from a shag, but we did see some wild black rabbits, got very close to a cormorant (I think) and took pix of some gull things (probably kittiwakes or fulmars, I later learned) nesting on an offshore stack. The more dedicated twitchers on board saw the last of the puffins and one bloke who went right across the island and saw a golden eagle and a hen harrier. There wasn't the extreme profusity of bird life that others have mentioned, but I guess it was a bit late in the year for that.
I am not any sort of bird watcher anyway: I went on the trip for a little adventure, and it certainly was that - bird life, sea life (did I mention the orange jellyfish?), but above all a calm peaceful all-day chug around some beautiful scenery that you can't see any other way. As even politicians apparently say these days, a great chillaxing kind of thing, and well worth the money.
Take food and drink (there's coffee and juice to buy on the boat, but no food), warm and waterproof clothing in case the weather acts up, and sun protection - hat, lotion: the UV bounces up off the water too.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.