I have been searching for an ideal light fixture to install at a cousin's house, and they live near the coast. They also want it to not harm wildlife, which limits the fixture options. Would a FCO wallpack in 35W HPS be good? It would light up an outdoor boat dock area.

I have been searching for an ideal light fixture to install at a cousin's house, and they live near the coast. They also want it to not harm wildlife, which limits the fixture options. Would a FCO wallpack in 35W HPS be good? It would light up an outdoor boat dock area.

LPS, in an FCO would be better for the wildlife.. And install a timer and turn it off when it's not needed, because in reality how often is the light used and needed at 3AM? You can also get either amber or Red LED's which are wildlife approved, I'm actually not near any coast but I'am pretty happy with the Feit PAR38/R/LED  lamp and it's certified...

If there is any sort of edge (low stone wall etc) around the marina, install something very small below this line, like a low mounted wallpack or multiple in-wall LED spots

Otherwise, where is the wildlife you want to protect, and what they respond to (the light source or the illuminated Earth) ?

If the life is on the ground - install an FCO. It may be better to install it on a pole off the house and not on the house :

 - On the house : The house blocks most of the light in one direction, but there is a brightly illuminated patch on the wall which might in itself defeat the point of FCO

 - On a pole : There isnt the illuminated patch on the wall, but the lantern and the illuminated area on the Earth are visible from more directions

If the life is in the water - consider to install it not at the house pointing towards the sea, but on a pole in the far end of the marina pointing towards the house, in which case its supposed to be not an FCO facing down but a floodlight facing forward, and add some "wings" around it (like on a theater spotlight) to block sideways light. This way it won't be seen as much from the Water

Install a step relay to control it, with few push buttons in the area to make it convenient to switch on/off as needed. If you use 24V signalling for the relays, you could go as far as locating a button in a place accessible from the sea without risk of electric shock

As much as some people dislike wildlife certified lights, this company has some awesome copper fixtures which are certified wildlife friendly https://www.pmlighting.com/ and this website is a pretty good resource for fixtures and mounting them http://myfwc.com/conservation/you-conserve/lighting/certified/ 

Could a motion-activated floodlight be a better option? They're only used when needed, but are boring compared to a HPS wallpack.

Well since they're only on occasionally I'd think they'd be fine, but you'd probably have to waterproof it. Honestly if it is like on a small pier I'd put up some of those kindof flattened hubcap/bell shaped incandescent lanterns and put in some lwer watage incandescents or filament LED's

I'd go for something like this and use this lamp if the light will only see occasional use (so power consumption won't be a major concern).

Here's a trickier problem, I want to select a fixture to potentially install at the beach condo. It's still a coastal area, and the sea turtles are a few hundred feet away.
They also need a lot of light, since the only fixtures there are a couple wimpy post lights and some LED fixtures for the covered parking area.

While they might not want a lower light level, there is Sea Turtle Protection Ordinances in Florida and they do carry penalties for violation and only like three areas have adopted a voluntary compliance the rest are in the law books, about the highest lumen output light you can legally get away with using is a 35 watt LPS in a full cut off down lighting mounted at about 8 feet in height, but they take time to warm up and are expensive and hard to find today, so you might be better to go with a red or amber LED and a motion sensor, and aim them away from the beach, The PAR38/R/LED are worth about $15 from Feit it's a bright light when used correctly and it's all of 6 watts and it's certified for use around sea turtles an it will run on most motion sensors, just get a few and mount them closer together.. And while you might think they won't catch you using a non-compliant light all it takes is you annoy a neighbor and they will find out about them or some people just out for walk to watch the turtles nest or make the trip to the sea to rat you out, it might take a while but they will nail you eventually, because your not going to be dealing with some redneck who's looking to pick a fight and will just take a 22 to your light in the middle of the night and you'll never see them again, your going to be dealing with people who will use the internet and social media,  and the laws and how to report violations are all easy to find online and they will let someone else solve there issues with your lighting affecting or potentially affecting the sea turtles and the people that come and visit carry ticket books and have the ability to issue a removal order and they carry guns and hand cuffs just in-case you don't want to comply to the first two options..

And going with any color other then red or amber when others around you are using red or amber lighting will also make your lights attract unwanted attention because they will stick out like a sore thumb in a sea of amber and red at night...