i personally like ladders to keep me interested, or repeating sets
but yeah, if you can swim that far striaght, you need to be working on speed.
50s, 100s, 200s at most right now.
there are a million and one ways to work them into sets.
sets with little rest
(5-15 sec
) will build endurance/threshold levels
sets with a lot more rest, 30 sec-2 min depending on distance will build top end speed.
work some of both in, much more of the first.
desending sets are also fun.
something like 4x100 on 2:00
(where you have 2 min to do the swim and rest, so if it takes you 1:30, you have 30 sec of rest
)
then 4x100 on 1:45
4x100 on 1:30
keep dropping time off the interval until you cant do it anymore.
some hard pull and kick sets are fun too and will help your swimming.
one like is:
good long warmup, mostly swimming for this.
main set x4
400 hard pull with paddles
200 hard kick with flipper
(alternate kicking on back, with board every set
).
for speed sets, i like to go one of two ways.
long sets of 50s, anywhere from 20-40 of them. mind numbing workout, but at least for me it works well. i keep rest about as long or just longer than the swim pace.
or, the other speed workout i like is something like:
4x100 on 2:30
(coming in around 1:05-6
)
4x75 on :45 rest
5x100 hard kick with flippers
10x25 sprint, 20 sec rest.
endurance sets a lot easier and are more limited to getting paces right and how creative you are or how much tourture you can endure on the boredom front.