Here is a nice speed endurance workout for you, have fun!
10min general dynamic movement.
10min @ 60% (easy talk pace).
5x30sec sprints with 1min active recovery (easy talk pace) between pieces. Stay in control, no splash at the catch, smooth through the water, pulling yourself to the paddle, not the paddle to you.
8 x 4min @ 80% (can’t talk pace) with 2min rest between pieces
10min @ 60% (easy to talk pace)