Another negative point for me is the angle of the seat. Unlike the Concept2, it has a slight backward angle, which makes it easier to maintain good form at the end of the stroke. Given that the Waterrower has greater resistance at the catch, it puts more pressure on the lower back at this point making it uncomfortable for people like myself with lumbar spine problems.
A third non-elastic handle return strategy is disclosed in US patent, "Gravity Return Rowing Exercise Device" (US9878200 B2, 2018) granted to Robert Edmondson. As stated in the patent document, the utilization of gravity (ie: a weight) to take up the chain and return the handle eliminates the inevitable variability of handle return force associated with an elastic cord system and thereby ensures consistency between machines.
Row for 1 minute applying as much power and force as you can, then take 1 minute of very light strokes for rest. That’s one rep. Complete 5 reps and then take a short break, no more than a few minutes, before moving on to the next set. Similarly, the goal is to hold the lowest split possible in the hard pieces. The prescribed stroke rates are 18, 20, 22, 24, and 26 for the first set; 20, 22, 24, 26, and 28 for the second; and 22, 24, 26, 28, and 30 for the third. 
Amateur competition in England began towards the end of the 18th century. Documentary evidence from this period is sparse, but it is known that the Monarch Boat Club of Eton College and the Isis Club of Westminster School were both in existence in the 1790s. The Star Club and Arrow Club in London for gentlemen amateurs were also in existence before 1800. At the University of Oxford bumping races were first organised in 1815 when Brasenose College and Jesus College boat clubs had the first annual race[14] while at Cambridge the first recorded races were in 1827.[15] Brasenose beat Jesus to win Oxford University's first Head of the River; the two clubs claim to be the oldest established boat clubs in the world. The Boat Race between Oxford University and Cambridge University first took place in 1829, and was the second intercollegiate sporting event (following the first Varsity Cricket Match by 2 years). The interest in the first Boat Race and subsequent matches led the town of Henley-on-Thames to begin hosting an annual regatta in 1839.[16]
In the patent record, means are disclosed whereby the chain/cable take-up and handle return are accomplished without the use of a spring or elastic cord, thereby avoiding the stated disadvantages and defects of this broadly used method. One example is the Gjessing-Nilson device described above. Partially discernable in the thumbnail photo, it utilizes a cable wrapped around a helical pulley on the flywheel shaft, the ends of this cable being connected to opposite ends of a long pole to which a handle is fixed. The obvious disadvantage of this system is the forward space requirement to accommodate the extension of the handle pole at the "catch" portion of the stroke. The advantage is that, except for small transmission losses, all of the user's energy output is imparted to the flywheel, where it can be accurately measured, not split between the flywheel and an elastic cord of variable, unmeasured resistance. If a similar system were installed on all rowing ergometers used in indoor rowing competitions, consistency between machines would be guaranteed because the variability factor of elastic cord resistance would be eliminated, and this would therefore ensure that the monitor displayed actual user energy input.