At high tide go upstream and fish the area of the railroad bridge, then work your way down through the marsh with the tide. I like an 8 or 9 weight for most of this fishing, though I'll use a 10 out in the surf. From June 20 on there is always a chance blues will be blitzing. I've found these conditions mostly around 5 AM when the ebb is at 8 or so. Big white deceivers do the trick, but I've had the most fun using poppers with a fast 2 hand retreive. You need wire for this, as the bank opposite the beach is very rocky and the blues are very good at biting and rubbing even the heaviest mono shockers. These are often big fish, in the high teens. In 6-8' of water with a strong tide you will find they can run a long way, and you'll need a powerful rod to keep them under control. A 10 weight is about right. You can use something lighter, but if it's crowded and your fish runs all over the place you won't make a lot of friends. The fish stay in the area through September. There are always a lot of sand eels in the water here, and I've had great luck with surf candies on a fast sinking line in the rip. The coastline from the Mousam north is quite rocky, and holds a lot of fish.
The Mousam River is locally known as a striper hotspot, though blues often visit. Most popular fishing spot is from Parson's Beach off Rte.9 in Kennebunk, though there are several other spots worth trying, such as the areas around the Route 9 bridge (parking here is limited.) Schoolies begin showing up at the Mousam around May 15th, the first ones being quite small (5 weight material). These early schoolies are suckers for a chartreuse clouser. The rip at this spot is quite strong, so sinking lines bring the best results. As the run heats up in the last week of May and first weeks of June the action can be furious - and the crowds can too. You need to get here really early to get a spot near the rip, but be careful trying to wade out too early, as the current is brutal and the dropoff well disguised. Actually, the entire beach, as well as the first mile of the river, holds plenty of fish, so there is no need to crowd the rip. The river itself is very pleasant to fish from a small boat or canoe. There is a small launch on the west side of the Rte.9 bridge.