There are two ways to get to the Isle of Wight by train. Both take 2.5 hours but offer very smooth connections between train and ferry, and return journeys at least hourly. You can usually stay till around 9pm on the island and still get back to London the same day.
1) Train from Waterloo to Portsmouth Harbour and then seacat (it goes from just next to the railway station) to Ryde. From here you get the charming island railway train (which is operated by old Waterloo and City Line tube stock) to Sandown or Shanklin. Both of these places are on the same magnificent five mile sandy beach that runs along the eastern side of the island. This is very pleasant swimming territory, with a shallow bottom and good breakers when the sea is a bit lively. Sandown is a bit more glitzy, with a pier and some smart 1930s style buildings. Shanklin is more villagey, but has an interesting coastline, particularly at the southern end where the cliffs get tall.
- Other things to do in Sandown include walking out to the chalk headland of Culver Point. The walk along the clifftop to Shanklin, though it passes suburban houses throughout, is also very pleasant with fine views, and you will find a seasonal cafe or two up here. South of Shanklin there is the wonderful coast path to Ventnor, which takes an hour or two and is a fascinating exploration of subtropical vegetation, hidden valleys and the curious jungle of The Landslip. Ventnor also has a small beach, with the town rising romantically up the hill behind it, and buses back from there to Shanklin are very frequent.
- Other things to do from Yarmouth include walking or taking the bus to The Needles (the rocky end of the Isle of Wight, or to Freshwater Bay on its south coast, which has a dramatic rocky cove (also swimmable), a pub and a tea room. Between The Needles and Freshwater Bay is the glorious clifftop walk along Tennyson Down, one of the finest promenades in England. From Freshwater Bay, there is also a pretty walk along the marshy Yar valley to Yarmouth (see SWC Walk 72 Yarmouth Circular). You can do all or any or this, get a very frequent bus back to Yarmouth, and be back in London by bedtime.