I spent 45 minutes total, 30 minutes running and 15 minutes swimming. My running included 5x the 30 -20- 10 second surge sequence. In the pool I do that as 55 leg pumps at 5K effort, than 35 at 1500m race pace effort, than 25 at maximum effort. That usually results in some serious quadricep burning and considerable aerobic stress. It usually takes me two or three minutes to recover from that sequence.
Than into a nice 15-minute whirlpool afterwards to make it a very pleasant morning.