Kayak 2:00:00 
Paddle to Greenhithe bridge and back at dead low tide. Felt sluggish most of the way, most probably due to shallow water.
Experimented with foam on seat to lift me up a bit. Paddled like that down to first yellow pole, then after meeting Sonja just past marina on way back, put it back in at first yellow pole and paddled home like that. Definitely notice a difference to stroke, but stretching to reach pedals.