Pool safety device for children

Um, if the house is at the beach how will you alarm the ocean?

Keep the doors locked! 

I would steer away from pool covers though unless they are solid and sealed, anything else becomes MORE of a drowning hazard if someone ends up on top of them and under the water.

Teaching water safety and getting swim lessons would probably be the best move.

We spend a lot of time at my in-laws beach cottage with a canal and dock in the back yard.  We have a 5yo and a 2yo - so you've certainly got more ground to cover.  First rule, they're never out of sight.  Second, they never go on the dock without wearing a PFD.  The 5yo knows this rule well.  So, if the pool is in a somewhat confined area, you could try the PFD rule until you're more comfortable with swimming abilities.

Swim lessons...    Honsestly, with the # of pools, lakes oceans etc here in my area, we decided it was a non option once our kids were about a year old.   You can take a lot of precautions with gates, locks etc, but there are too many stories every year for me to not have best piece of mind which is child knows how to get to the side of the pool/steps etc.    Might be too close a time to get these lessons in before visit, but cant express the need to do this at very early age.   Our kids were swimming independently before 2 yrs old.   I was too scared to drop my own kids in so had an instructor put up with their initial crying and fits.   They stopped crying WAY sooner for other people vs mom and I.   

Good luck.

http://babygate.net/

this is the company we use for all of our pools

Fence, fence, fence.  We just had an 18 month old boy in our neighborhood drown.  There was no fence around the pool.  It was absolutely heart breaking.  My inlaws just moved into a home in our neighborhood and the pool didn't have a fence.  My wife and I ended up paying to put in a fence.  We had a mesh fence installed similar to what you see here: www.poolbarrieraz.com.  I can't imagine not having a fence with even our 3 year old. 

X2  We used the mesh fence til our kids were strong enough swimmers/old enough to take it down. Just make sure you get one with a self closing gate. Some people choose to just open and close a section as they enter or exit. All it takes is to forget one time or get distracted for tragedy to occur.

COMPLETELY agree with this. Our kids were never allowed in the yard unless we were there to watch. Fence/alarm just adds another layer of safety.

This is mandated Federally? I thought this was determined locally.

The Consumer Products Safety Commission has a lot of good information on their site.  Check out http://www.poolsafely.gov/

Hope that helps.