im 5'Ƈ' 166
eat
breakfist
lunch
dinner
ONLY.
swim 4000 yards 5 days a week.
walk 2 miles 5 days a week
bike 5 miles daily.
do 400 crunches daily.
will it help to get me to 124 by the end of the summer?

not enough info

If you're going to be doing that much exercise, you'll need to eat more, by including some healthy snacks through the day. Weight loss is entirely dependent on there being a calorie deficit (more calories burned than consumed) but you still need to eat enough calories to give you the energy to exercise, otherwise this whole plan of yours will collapse very quickly.
Consult a professional - they know what they're doing.

thats a lot of weight to lose in only a little time
no body really knos if it will help but i bet if
you keep trying then you can do it! try other things
like watching wat you eat as well.
??? jetta

No one can tell you if you'll be 124 by the end of the summer, because you didn't give the exact daily caloric amount in the food you plan to eat. If anyone says yes or no, it's not founded on anything but a guess. Unless you're already active, it seems like you're jumping into too much exercise. You might get fed up and exhausted and completely stop if you approach it this way. I'd save the crunches for after you've reached your goal weight, because rather than reducing your waist, they'll build muscle underneath the layer of fat and your midsection will actually get larger. If you can, I'd switch the "only breakfast, lunch, and dinner" plan for 5 or 6 small meals (200 calories or so a piece) a day. This will keep your blood sugar level stable and help prevent binging it'll also keep your metabolism up.

swimming burns around 100 cal per hour
walking 2 miles burns around 100
bike 5 miles burns around 500-700 depending on pace
400 crunches about 100 cal
lets assume your meals are around 400 cal each
so 400x3=1200 - 800= 400
1200 +400= 1600
you will definatley lose weight making a deficit of 1600-2000 a day you could lose up to 2 pounds every 2 days but be carefull you to not over strain your self hun.

Maybe, if you actually commit to it.
Also, don't starve yourself.