Aruba
Expect a half-day boat trip where you motor out to spots where wild dolphins are often seen. When conditions are good you'll get 20-40 minutes of dolphins riding the bow wave, jumping, and playing alongside the boat. The crew usually slows down or stops when they appear so you can watch and take photos. Most trips also include snorkeling on a shallow reef afterward. It's not a swim-with-dolphins encounter; you're observing from the boat. The ride can be bumpy if the trade winds are strong, and seasickness is common on the way back.
Best time is April through October when the water is calmer and dolphin sightings are more consistent. December to March can be windier with rougher seas, though you might still see dolphins. Expect to pay around $60-110 per person depending on whether you choose a basic tour or one with lunch and open bar. Private or smaller-group options push toward the higher end.
Tip: pick a smaller boat (under 25 people) if you can; you get more space at the railing and better photos. Skip the ones that advertise "guaranteed" dolphin encounters; nothing is guaranteed in nature and those tend to be the bigger, louder party boats. Bring your own motion-sickness meds and a waterproof phone case.