Decided to do a quick last minute one day visit to Provincetown. Booked my round trip ferry ticket online (it's cheaper to book a roundtrip than two one-ways). Weekends and holidays sell out early but I went mid-week and didn't have any issues booking a day in advance. There are a few different boats from BHC departing Boston so ask around to make sure you're lining up for the correct one. You can pull up your ticket on your phone, no need to print out.
People start to line up pretty early (I went about 30 minutes before departure and the line was quite long but moved quickly). The earlier you line up, the better chance of getting to sit wherever you want. There are indoor air-conditioned and outdoor areas, plus a bar and restrooms on board. The outdoor area in the front of the boat is very windy but the rear is more pleasant. The ride was about 80-90 minutes each way, and I had full cell phone service throughout (T-Mobile). Everyone on board seemed friendly and chatty - naturally since they're on vacation. A mix of gay guys, families, young and old from all over. You see a little bit of land in the distance throughout the journey, and the boat ride is really smooth. I get seasick easily but didn't have any issues at all. The 9AM departure was on time but the 330PM return was a few minutes delayed. The crew is friendly and mostly stays out of your way.
Overall it's the best way to get from Boston to PTown. Faster than driving, cheaper than flying, and easier than swimming!
Tip: Wear a lot of sunscreen if you plan to sit outside. Hats might get blown away if you're at the front of ship, and you won't realize your skin is burning due to the moisture in the air and the wind.