Float trips on the Thames

Depends on how much of a boat trip you want. The are a number of ferries that run on the Thames. Will not see much from the ferries.

We love riding the Thames Clippers. Sitting in the open area at the stern, one has a great view. You can ride different sections of the river on different lines, covering the distance from Putney to Greenwich and beyond. We like to walk one way on the Thames Path and ride back.

https://www.thamesclippers.com/route-time-table/book-now

Thank you Lola, that sounds great. I'll look into it.

If you are going to visit Windsor, you can get a short cruise on the Thames near the bridge that crosses over into Eaton. You get to see the back of Windsor Castle, and a good bit of the countryside surrounding Windsor. Its a nice way to spend some cooler time on a hot summer's day.

Another vote for the Thames Clippers.

Best ride: after seeing Westminster Abbey, board the Thames Clipper going east, to Tower Hill to see the Tower of London. Then board the boat again going east to Greenwich to see The National Maritime Museum and the Cutty Sark ship.

Great thing about the Thames Clippers is that they take the Oyster card. Just tap in as you get on the boat. Remember to tap out each time you get off the boat.

Same for using the Oyster card on the tube. Tap in, tap out.

You don't only have to choose between the London Eye and the Thames boats to passively see the sights' highlights - there are several rooftop gardens now, most free and very scenic.

Tate Modern
One New Change
good views from the restaurant top floor Peter Jones, Sloane Square
Japanese Garden on top of SOAS, closed temporarily
Shard - I'll never go up there for philosophical reasons, and very expensive, but the highest in town
At the top of the Walkie-Talkie Building is Sky Garden, perhaps the best of the bunch, IMHO

And to answer questions you have about the Oyster card:
Yes, Oyster is basically a debit card.
There are "ATM" type of machines all over London where you can purchase them.
Every tube (subway) station has several of these machines.

There is a keypad where you choose the pound amount you want to put on the card.
Choose 20 pounds, push the button, insert your credit card (or cash) into the slot below.
It will spit out an Oyster card that looks similar to a Mastercard or Visa.

You take this and tap it on the "pad" as you go through the turnstile to get on the tube (subway).
As you finish your journey on the tube, and exit the train car, there will be another turnstile, tap the card on the pad, then walk out of the station to the street.

You can also buy Oyster card at small grocery stores around London.
There is a wall of Oyster card machines at Heathrow airport, so you can get one as you are arriving.

The amount on the card can be added to or "topped up" as you use it and the balance gets low.
This is also done at one of the machines.

Oyster card is also used to ride city buses in London, and the Thames Clipper boats.
Tap in on the bus, but do not tap out once you leave.

I hope this helps!
Rebecca

P.S. There are many videos on YouTube demonstrating the purchase and use of the Oyster card.
Just do a search at YouTube and you will find dozens of videos.
They are quite helpful to the first time visitor to London.

Note that a ride on the Thames Clippers is more expensive than a Tube ride, but you do get a discount for using Oyster. Each time we queued up for the clipper there was an agent going around checking Oyster Cards to make sure there was sufficient £ on it to cover the ride.

Thank you everyone with your suggestions and advice.
Rebecca, I will go to YouTube as suggested. Your explanation regarding Oyster Cards was very helpful and informative.

You are most welcome. Glad to help.

We did the London Eye and then did a cruise on the Thames to Greenwich. We enjoyed it very much and I would recommend it.