The few posts seemingly about different conductivities possibly "bending" signals are interesting to me.
I was checking, and found a couple examples that are along the lines of what I was wondering about. Let's say I was to take a decent radio & antenna with me to a beach or pier, like at 32°44'59"N 117°15'33"W for example.
In Russia, there's a 1 MW (or 500 kW - don't quite understand what the listing on asiawaves.net means when it says "500-1000 kW) station on 234 kHz, at approximately 59°42'51"N, 150°11'31"E. The total path length is about 4383.13 miles or thereabouts. Tracing back along the path from the transmitter site, there's 191.1 miles of land, then 155.06 miles of saltwater, 56.17 miles of land, 80.04 miles of saltwater, and 313.57 miles of land across a peninsula. Then, except for 9.25 brief land miles it's all saltwater (633.56 miles) until you hit an island off the coast of Alaska, which is 63.34 land miles along the path. Then,130.94 miles more saltwater, then a bit of Alaska sticks out putting 56.47 miles of land along the path, then it kind-of hugs the coast (trading inlets, land jettings out, etc) for 49.27 miles, then another peninsula takes 21.42 miles. Then 50.12 miles of water, 78.42 miles across another peninsula, 39.68 miles more saltwater, and 62.91 miles across an island south of Alaska. Then, it's more saltwater (1718.78 miles), until you hit the northern coast of California, then 590.19 miles of land to Huntington Beach (SE of Long Beach), then the final 75.78 miles is saltwater.
However, from the transmitter site, if you go 4.15 miles SOUTH, you hit saltwater MUCH quicker. Then, you go southeast about 658.07 miles to get to the southern tip of that peninsula sticking south out of the eastern end of Siberia. At this point you're about 850 miles or so off the supposed path, but it's all saltwater, except for 3.04 miles across a small island (but deflecting about 3.5 miles east would skirt that island). Then, from there, it would be 4350 miles of saltwater, or possibly a few hundred miles farther because you'd have to skirt south of the Aleuitan Islands and west of the California coastline.
Another example would be the 200 kW station on 576 kHz at Yangon, Myanmar, at about 8366 miles. The predicted path takes it back through eastern Asia over almost 3600 miles of land, but if you go just 7 miles south you get to a fairly wide river. Then, it's another 24 miles or so along the mouth of the river, then you skirt south around 1200-1300 miles along the west coast of Malaysia, squeeze between there and Singapore / Indonesia, then turn east, avoiding various islands along the way. Eventually once you get past the Philippines about 2000 miles or so later, it's pretty much open ocean back to the receive site.
Also there's a 50kW on 567 in New Zealand about 6693 miles away, whose transmitter is just 0.2 miles from the coast via the shortest path to the coast (northwest from tx to shore). However, the direct path takes you northeast along about 160 miles of land before you hit open ocean. If you go to the coast, though, then you could skirt south about 50 miles or so around that part of NZ, then it would be saltwater the rest of the way.
I'm guessing, though, it would be a bit
too ambitious to attempt to DX a station on the coast of the Mediterranean by way of the canal separating Egypt from Saudi Arabia (forget the name), the Red Sea, Indian Ocean (passing south of India), go between Malaysia & Vietnam, through the Philippines, then open ocean back to the USA west coast ... OR, receive a station on Europe's west coast by skirting north along the northern coast of Russia (along the Arctic ocean), down through the Bearing Strait, then down & across the pacific back to the receive QTH.

That'd be an all-saltwater path, but the great circle path in both those cases makes it theoretically trans-Atlantic reception (you'd have to cross the entire continent of North America), not Trans-Pacific-And-Indian-Ocean or Trans-Pacific-and-Arctic reception.

I almost wonder if Mauritius (an island east of Madagascar) might be doable, though, especially if there was a 500+ kW with a 1/2-wave or taller antenna below 600 kHz? The great circle path from the proposed listening location would be about 11542 miles, via Asia, the Arctic Ocean and western North America. It's possible to get an all-saltwater path, though - east across the Indian Ocean, between Australia & Indonesia / Philippines, then across the Pacific (avoiding Hawaii), for a path length of about 12,600 miles.
Or, there's a small island at about 37°51"S 77°35"E, about 11544 miles distant, which does have almost an all-saltwater path (except for having to skirt around the southeast part of Australia). Unfortunately, that island, according to Google's satellite view, looks uninhabited, so there's virtually no chance of a high-power, low-frequency, large-antenna MW or LW station being there.
Anyhow... a little bit ago I briefly went and tried to check out some of the eastern Asian & Australian tuners, but couldn't get anything across the pond that I could identify. Hong Kong DX's fixed selectivity was too broad, Sydney's was kind-of noisy (and had locals near some frequencies I wanted to try, and I couldn't get any MW at all on Gold Coast... then when I was trying Sydney again someone came and started tuning 3.5 MHz CW after I'd said I was looking for MW stations.

A few weeks ago I thought I heard a trace of 760 KFMB on one of the receivers, but I can't remember which one now (think it was an Australian). Other targets I'd like to try include 640 KFI, 660 KTNN, 680 KNBR, 710 KSPN, 720 KDWN, 740 KCBS, 760 KFMB (again), 770 KKOB, 780 KKOH, 810 KGO, 830 KLAA, 840 KXNT, 910 KECR, 1000 KOMO, 1020 KTNQ, 1040 KURS, 1070 KNX, 1090 XEPRS, 1110 KDIS, 1130 KSDO, 1160 KSL, 1170 KCBQ, 1210 KPRZ, 1240 KNSN, 1320 KKSM, 1430 KMRB, 1520 KOKC, 1530 KFBK, 1540 KMPC, 1560 KNZR, 1580 KMIK, 1700 XEPE. (This is of course not an exhaustive list. Also some have fairly low transmit powers (a few kW down to maybe a few dozen watts), but their groundwave still strongly reaches the shore via either a directional antenna or being within a couple miles or so of the shore, or both.)
Also I went to try that Atlantic DX receiver earlier, but it was offline.
One thing I think would be an ultimate DX thrill would be saltwater groundwave DX of a station about 12,450 miles away - for example receiving a 2 MW station on 153 kHz (with an antenna efficiency of at least 510 mV/m/kW) whose transmitter site is right on the beach. (An even more exotic catch might be a 15.205 or 15.209-compliant signal around 30 MHz across an all-sand-and-granite path, but I believe that would be impossible.) Any idea of what global tuner receivers might give me the best chance of doing that (not counting of course the impossibility in the parentheses previous sentence)?
I've also been wanting to try a few of the east coast receivers (like Southern New England & Buffalo, NY) around their local noon, but I never can seem to be around to do it. For example, I'd like to compare their reception of stations like 660 WFAN, 770 WABC, 810 WGY, 880 WCBS, 1020 KDKA, 1030 WBZ, 1080 WTIC, 1090 WBAL, 1180 WHAM, 1210 WPHT, 1520 WWKB with my barefoot SRF-59 coastal saltwater reception of stations like 990 KTMS (< ~20 watts ERP toward my proposed test location, ~ 185 mi distant), 1290 KZSB (500 watts, ~182 mi), 1340 KCLU (650 watts, diplex KZSB), 1490 KSPE (1 kW, triplex KZSB/KCLU).

I would expect, for example, the southern NE receiver to get at least a 120 dB better S/N on WPHT than my pocket radio would get on the aforementioned 990 KTMS, but due to the extreme difference in ground conductivity I'm somewhat prepared to be surprised. (BTW last time I tried KTMS from within 1/2 mile of the beach on the PL-606, it was definitely an easy armchair copy using only the stock ferrite, in spite of maybe ~15 watts ERP over about 185 miles or so, and a transmitter site several miles inland. The station's actually 5 kW daytime but I'm in a deep null.)